Worship
The Catholic Encyclopaedia at http://www.newadvent.org\cathen\15710a.htm states as follows:

The word worship (Saxon weorthscipe, “honour”; from worth, meaning “value”, “dignity”, “price”, and the termination, ship; Latin cultus) in its most general sense is homage paid to a person or a thing. In this sense we may speak of hero-worship, worship of the emperor, of demons, of the angels, even of relics, and especially of the Cross. This article will deal with Christian worship according to the following definition: homage paid to God, to Jesus Christ, to His saints, to the beings or even to the objects which have a special relation to God.

There are several degrees of this worship:

if it is addressed directly to God, it is superior, absolute, supreme worship, or worship of adoration, or, according to the consecrated theological term, a worship of latria. This sovereign worship is due to God alone; addressed to a creature it would become idolatry.
When worship is addressed only indirectly to God, that is, when its object is the veneration of martyrs, of angels, or of saints, it is a subordinate worship dependent on the first, and relative, in so far as it honours the creatures of God for their peculiar relations with Him; it is designated by theologians as the worship of dulia, a term denoting servitude, and implying, when used to signify our worship of distinguished servants of God, that their service to Him is their title to our veneration (cf. Chollet, loc. cit., col. 2407, and Bouquillon, Tractatus de virtute religionis, I, Bruges, 1880, 22 sq.).
As the Blessed Virgin has a separate and absolutely supereminent rank among the saints, the worship paid to her is called hyperdulia.
In accordance with these principles it will readily be understood that a certain worship may be offered even to inanimate objects, such as the relics of a martyr, the Cross of Christ, the Crown of Thorns, or even the statue or picture of a saint. There is here no confusion or danger of idolatry, for this worship is subordinate or dependent. The relic of the saint is venerated because of the link which unites it with the person who is adored or venerated; while the statue or picture is regarded as having a conventional relation to a person who has a right to our homage -- as being a symbol which reminds us of that person (see Vacant, Diet de théol. cath., s.v. Adoration, and authors cited in bibliography; also ADORATION; IDOLATRY; IMAGES, DEVOTION TO THE BLESSED VIRGIN MARY).

From this it can be seen that the protestant concept of who can be worshipped is far narrower that the Catholic concept of worship. There are four different types of objects able to be worshipped in the Catholic church:

God and person of The Trinity
Mary
Saints
Objects (e.g. relics)

So each will need to be examined separately.
They will be examined according to the guidelines in the introduction to this book
First the definition of adoration from the Catholic encyclopaedia at http:\\www.newadvent.org\cathen\01151a.htm:
Adoration

In the strict sense, an act of religion offered to God in acknowledgment of His supreme perfection and dominion, and of the creature’s dependence upon Him; in a looser sense, the reverence shown to any person or object possessing, inherently or by association, a sacred character or a high degree of moral excellence.

Adoration can be given to others apart from God and this is the danger of worshipping things or persons other than God in that it can turn into idolatry
Veneration
The Catholic encyclopaedia does not define veneration so the Wikipaedia was consulted at http://en.wikipedia.org/wiki/Veneration and it explained veneration as follows:

Veneration in Noto (San Corrado)In Christianity, veneration (Latin veneratio, Greek d????a dulia), or veneration of saints, is a special act of honoring a saint: a dead person who has been identified as singular in the traditions of the religion, and through them honoring God who made them and in whose image they are made. It is practiced by the Eastern Orthodox Church, the Roman Catholic Church, and some members of the Anglican Communion, Veneration is often shown outwardly by respectfully bowing or making the sign of the cross before a saint’s icon, relics, or statue. These items may also be kissed.
In Roman Catholic, Orthodox, and Anglo Catholic theology, veneration is a type of honor distinct from the worship due to God alone. Church theologians have long adopted the terms latria for the sacrificial worship due to God alone, and dulia for the veneration given to saints and icons. Catholic theology also includes the term hyperdulia for the type of veneration specifically paid to Mary, mother of Jesus, in Catholic tradition. This distinction is spelled out in the dogmatic conclusions of the Seventh Ecumenical Council, which also decreed that iconoclasm (forbidding icons and their veneration) is a heresy that amounts to a denial of the incarnation of Jesus.
Now, the Roman Catholic tradition has a well established philosophy for the veneration of the Virgin Mary via the field of Mariology with Pontifical schools such as the Marianum specifically devoted to this task.
In Hebrew the word for honoring a person such as a king or prophet is, which is the same word for worship of God[4]. Examples of such worship of or honoring men are demonstrated in 1 Kings 1:23 where the Prophet Nathan bowed  to King David:

I have examined Mary and the Saints earlier in this book.
I examine relics in section three
The question to ask is why do Catholics venerate anyone?
The statement from the Catholic encyclopaedia above states:

In Roman Catholic, Orthodox, and Anglo Catholic theology, veneration is a type of honor distinct from the worship due to God alone.
and
When worship is addressed only indirectly to God, that is, when its object is the veneration of martyrs, of angels, or of saints, it is a subordinate worship dependent on the first, and relative, in so far as it honours the creatures of God for their peculiar relations with Him;

In a nutshell, saints are venerated because of their relationship to God (How they lived on earth as His follower) and not because of who they are in their own right.  It is a different type of worship than God is given as it does not worship them as God bur respects them as people who have lived lives worth following.
There is nothing in the Bible stopping you honouring a person dead or alive and showing respect for they way they live and being inspired by their lifestyle.
In a sense it is like anyone showing respect and deference to people like Jim Elliot, Hudson Taylor or other great missionaries and Christians and wanting to live like they did for Jesus.  In other words their life style encourages you to follow Jesus at any cost.
So in this respect, if Catholics venerate their Saints in the same was as protestant their heroes of faith there will be no difference in the way they approach these Godly people, either as Catholic or Protestant.  There will also be no idolatry in any form.
The danger is when these people are prayed to and asked to do the things God should be doing or credited with God has done then idolatry occurs.  Praying to saints is the subject of an other entry in this section so it will not be discussed here.
Veneration of Objects
The Catholic encyclopaedia summarizes the veneration of objects as follows:

In accordance with these principles it will readily be understood that a certain worship may be offered even to inanimate objects, such as the relics of a martyr, the Cross of Christ, the Crown of Thorns, or even the statue or picture of a saint. There is here no confusion or danger of idolatry, for this worship is subordinate or dependent. The relic of the saint is venerated because of the link which unites it with the person who is adored or venerated; while the statue or picture is regarded as having a conventional relation to a person who has a right to our homage -- as being a symbol which reminds us of that person
Objects associated with holy people are respected (venerated) because of this association.  The problem arises when these objects are looked to for the working of miracles so that they are looked to in their own right and the saint is honoured for the miracles that occur and not God.  This is the problem with canonisation in the Cathodic church that saints must perform two miracles, and be given credit for them and not God.
When objects are given special attention because of their relationship with saints (canonised holy people) then these objects take in importance because of their association with a person and not with God which is a form of idolatry.

The Catholic Catechism states as follows:

2132 The Christian veneration of images is not contrary to the first commandment which proscribes idols. Indeed, “the honor rendered to an image passes to its prototype,” and “whoever venerates an image venerates the person portrayed in it.” The honor paid to sacred images is a “respectful veneration,” not the adoration due to God alone:
Religious worship is not directed to images in themselves, considered as mere things, but under their distinctive aspect as images leading us on to God incarnate. the movement toward the image does not terminate in it as image, but tends toward that whose image it is.

The footnotes referred int he above statement to say as follows:

70 St. Basil, De Spiritu Sancto 18, 45: PG 32, 149C; Council of Nicaea II: DS 601; cf. Council of Trent: DS 1821-1825; Vatican Council II: SC 126; LG 67. 71 St. Thomas Aquinas, STh II-II, 81, 3 ad 3.

It is to be noted that the references are the comments of men and not The Bible so do not carry the authority of scripture .
It is not that this veneration of saints or objects breaks the commandment against idolatry as this no longer applies (Act 15). The question is what is in the heart of the person as they approach saints and Mary and how it affects the Lordship of Christ in their heart.
If they can keep Christ as Lord in their heart and still give reverence to Godly people the way The Catholic church says it should be made and appreciate the relationship of objects to them or God without displacing Christ as Lord of their heart then they have done nothing wrong as it is the heart attitude to Jesus that is important not the way it is expressed.  The danger is that these can too easily displace Jesus in their heart and become idols.
Worship, Summary
It does not matter how, when or where you worship God as long as it is not:

Idolatrous (displacing the honour and worship due to Jesus)
Breaks the Law of Love causing another to sin or
Does not contravene The Bible in some way

God looks at the heart and not the actions and is not concerned what others think a person should do.  If your desire is to worship Jesus alone then other errors of faith you do not know about will not hinder your worship being accepted by Him.
Written out prayers and devotions
Should we use written out prayers and, devotions? God does. They are called Psalms in The Bible.
There is no thing wrong with written out prayers and devotions providing they only focus on a member of the God head. Any thing else is idolatry.
The other danger is to use them too often so they become a ‘habit’ and like a rote exercise.
Another danger is that the preparation of them can become centralised and legalistic so as to inhibit individual expression of prayers, either in public or in private,
A good devotion can encourage you in your Christian walk. The Holy Spirit is your guide in your Christian walk but He will use devotions of any type or source that focuses on the Godhead to help you in your Christian walk
An example of a devotion are the Stations of the Cross that is used by the Catholic denomination.  It focuses on Jesus and challenges your altitude to Him, His sufferings and His requirements of you. Pope John Paul II rewrote the traditional version so that it is now all Biblical.
The Stations of The Cross is really like an order of service with devotional points. Other denominations do similar but usually focus only on one thing like The death of Jesus (Good Friday), or His resurrection (Easter Sunday). Christmas is also celebrated but in the wrong month as the shepherds were in the fields and that is in June, July as it snows in December and there would have been no room in the barn for Mary and Joseph.  Perhaps we should celebrate Christmas in June to remove it from the pagan festival it has become and use the December celebration for evangelism.
The reaction against ritual has meant that pomp and ceremony honouring Jesus and which shows to the world that He is King, is not done as often as it should if at all. Satan knows the benefit of parading his kingdom and it is a pity Christians do not parade their faith and proclaim. Jesus as King as openly as Satan parades his world system.
The older denominations, such as the Catholic and orthodox still know this but Satan has apparently been able to hobble the modern denominations.  They hide the Kingdom in buildings, so that in some ways they have become an insular, secret type of society to those outside the modern church system.
The Kingdom of God does not hide.  It confronts the kingdom of Satan (world) in the open and defeats his works even if only in part, for a time.  Its manifestation and authority is seen openly and not hidden in a building.
In all things be led by The Holy Spirit and then you will proclaim The Gospel of The Kingdom of God, demonstrating it in a way that people will see it and come to you to learn of it.
So do we use written devotionals and orders of service?
Yes!  As long as they worship God and demonstrate, proclaim and teach The Kingdom of God, otherwise they are man’s work and useless for The Purposes of God Unless under they have been done under  the Guidance of The Holy Spirit in which case they will be for the purposes of The Kingdom of God any way.