If you do not know how to shoot a Shaker then you had better learn because it is an essential skill a Shaker Pilot must have. There are pilots who can dodge good placement and if yours is not aimed right then you are easy meat for these pilots. Prime rule: Shoot the Shaker where the other pilot is headed, in front of him, lead him. Remember lag?  Another newbie goof is shooting the Shaker at the other pilot.  Never shoot at someone.  Shoot at the floor, ceiling, or walls in front of him.  If he is moving from side to side, try to fake him out.  You can also aim it right under him if he is not moving or seems indecisive.  The initial blast will kill him, you can't dodge that {D2 only, There is no big blast splash in D3}.  Never hesitate to fire more than one Shaker at a pilot. A good pilot can dodge one Shaker, but it is much more difficult to evade 2 of them.  For a really good Shaker pilot you had better be ready to fire all you have. The likes of Uncle Smitty {Old D2 Shakerhead} can even dodge 4 or 5 Shakers fired at him. 

Most of the time you will find yourself with only one Shaker and several Megas, "the Pocket Pistol".  I love the Mega in a Gig2 game.  {It is just as good in D3 if used right} When Gig2 is set on Ace or Insane the Mega is a deadly missile.  I will most always follow a Shaker shot with a fast Mega shot.   And most of the time the Mega scores when the shaker failed.  Shaker placement is an Art and it takes a lot of game play to learn.  I still have not refined it to the point where I feel I'm good at it {Not even today in D3 am I satisfied with my placement} . Juice {Another old D2 Shakerhead} is the best placement pilot I have played.  He can cut your guts out with precise Shaker shots that you will find impossible to dodge.
It always amazes me to see a pilot survive a Shaker shot in to a fuel center, but it happens, a lot!  I will always, if I have them, fire two Shakers in to a fuel center.  One in each entrance.  Even then I've seen pilots fly out unharmed.  One other thing, after you have aimed and fired that perfect shot, you had better be ready to receive one back.  If I know I'm a goner I will try and fire all I have.  
Defense!   Yes we have all heard that a good defense wins games, and that holds true in Descent3 as well.  When I make a offence move toward another pilot I am already going into a defense move almost at the same time.  Expect the counter, because it will be there. So be ready for it. Defense!!!

Be Smart!

Lets not forget one of the deadliest missiles in the Gig 2 level, the Smart Missile!  I always enjoy a number of kills each game with Smarts.  I love the sound they make with a  direct hit on an opponent.  It is the most satisfying sound in the game as well as intimidating as hell on the one that received it. { The Smart is not as good in D3 as it was in D2, but don't discount it.}  I have seen more pilots leave the game after a direct hit with a smart missile than any other.  There are several ways to use Smarts and their all good ones.  Fire them into hallways, tunnels, and fuel centers while on the move, I'm often rewarded with the sound of metal and a kill.  I sometimes traverse through tunnels with Smarts selected over Shakers or Megas because they will not cause me to kill myself if I am surprised.  Don't ever expect me to fire just one smart.  If I have them, and I usually do, you will see 2 to 5 on your butt.  :)  I  will also be afterburning to beat hell.  If you're quick, or you hear the other guy coming, releasing that Smart at the right moment will sometimes greet him head on.  This death is faster, and cheaper, than a Shaker hit.   Another tactic I use after firing all other missiles at the other pilot, is to lay down a fast pattern of smarts in close, usually 4 to 5 of them.  Only the best pilots will escape a good pattern of 5 Smart Missiles.   Ok,  all I'm saying is never underestimate the Smart missile.  Especially in the hands of someone who knows how to use them.  The Smart is in the Game.   Learn how to use it yourself.