Each Banshee is also equipped with a Banshee Mask that amplifies the Banshees' warcry, overwhelming their enemy's central nervous system with psychic energy, causing a temporary paralysis that enables the Howling Banshee to always strike first.

Howling Banshees are best used against opponents that have an armour save better than 4+. Pitting the Banshees against lower armoured foes is a waste of points. The only exception I can think of to this, is when enemy troops are in cover, as is the case, quite often, when fighting the Imperial Guard.

When fighting against a massed foe such as the Imperial guard, be careful when assaulting squads that are near each other. The Banshees will probably win the first round of combat and the enemy will probably break and run (due to their high losses).  It is imperative that the Banshees don't sweep into other enemy squads, when they are pursuing a defeated squad.  Unless of course you want to draw a lot of fire away from the rest of your army.

To avoid sweeping into other enemy squads, it is a good idea to assault more than one squad at a time, so that the Banshees don't sweep into other enemy squads and get shot into pieces. Another reason to attack more than one squad (this assuming that the squads aren't more that 10 troops each) at a time is to make sure that the Banshees don't get caught out in the open, ( as can happen if they destroy their foes or the enemy runs away through their own troops) waiting to be shot.

If you are using the Banshees with some form of transportation and you wish to assault just one enemy squad, it is wise to keep the broadside (so it can't get shot or assaulted in the rear in the enemy's next turn) of the transport close (less than 5") to the squad that is to be to be assaulted so that if the Banshees wipe the enemy squad out, they can consolidate (3") to within 2" of the transport and re-embark into it.   That last tip was suggested to me by Allen Brokken (BrokkenA@Missouri.edu)

Against armies that are hth specialists, it's not wise to use Banshees, as they may win the first round of an assault phase, but they won't last past the next turn. Using Banshees against Orks or Tyrannids would only be playing into your enemy's hands, as you would be fighting in a way that favours them. Against such enemies, it is better to shoot them from a distance than to engage them in hth.

Because of the Howling Banshees' low strength, it is best if Banshees outnumber higher toughness adversaries such as Space Marines.  The Banshees low strength also makes it an unwise choice to use them against high toughness foes such as Space Marines on bikes.   It is very interesting (although depressing) to see the results of an assault of 10 Howling Banshees on 5 Space Marines on bikes, as simulated on the hand to hand combat calculator.

Like most Eldar troops, Banshees are fragile and need to be screened or transported to get near enough to the enemy, to be of any use. It is also wise to use Banshees in combination with other troops such as Fire Dragons, so that the Dragons can soften up the enemy and the Banshees can mop up the survivors. An Exarch is a valuable addition to a squad of Banshees, as their high leadership and extra attack will come in very handy during an assault.

If the Banshees are being dropped off by a transport, it is a good idea to try and position the transport so that any enemy troops that break will have their retreat blocked, so that you can take advantage of the crossfire rules and destroy the enemy.

Banshees make a very good bodyguard for Independent Characters as they represent an excellent deterrent against deep striking troops and assassins.