When you are killing a pill, never allow yourself to take more hits than necessary. Fire just enough shots to kill the pillbox, then turn and accelerate simultaneously to avoid stray shots. You will learn as you play to guess when you have fired enough to kill the pillbox (it takes 15 shots, but it's impossible to count off the 15 in the middle of a game). It is also convenient to know how a pillbox's appearance indicates the number of shots needed to kill it. Look at the illustration at the top of this guide for an example.
If you are playing with invisible mines, always shoot the square you are planning to build on before you send your builder out. Also make sure that the pillbox you are building near is not shooting at you, unless you are positive you can time the building right.
If you are having trouble figuring out where to build walls so that the pillbox will shoot them instead of you, use the cursor to count off the squares. Learn how many squares away you need to coordinate your block squares or to position your tank, then count them off during actual play. It may seem slow at first, but it will get easier with experience. Eventually you should be able to get in the correct position without counting.
If you use enough wall / pills to absorb all the shots from a pill (usually 3 walls will do it with lag) you can keep firing at the dead pill and kill a foolish enemy's builder.
If you are in a game on a map with a lot of walls, use neutral pills to clear buildings away from the bases so that you won't have to do it yourself later. Shoot the neutral pill until it is near dead, then let it shoot through the buildings around your base trying to get to you.
When you see someone set down a couple of pills to take your pill, use their setup against them. There is nothing more satisfying in a game than taking the two pills your enemy thought they were going to use to take your one before they know what's hit them.