In order to keep you opponent from being able to accurately predict your serve there area handful of different foot positions you should employ.
The first and most common amongst tod's elite racquetball players is the diagonal two-step.
Next is a variation above the above foot positioning except you take one step towards one of the walls with the back foot then drive forward with the lead foot (the one in front!).
The next stance would basically be your standard forehand stance, except you take two little steps before blasting the ball as if you were hitting the ball like a traditional forehand. Just make sure you get the ball past the foul line!
These are the most common foot placements for serving. While these are the most popular it is not uncommon for players to make hybrids between these stances when serving in order to make it difficult to predict how they will serve the ball.