To keep shots low, I recommend either holding R2 (for PS2) while powering up, or just simply not hitting the ball to hard, but placing it from distance. The keeper will not take any steps after you make a shot, so exploit this by positioning your shot as close to the post as possible.
From close range, the ball will automatically spin but there is no manual way of doing it.
I find the best way to do volleys are by crossing it normally to a player using off the ball, then instead of heading towards goal, head back outside the box toward one of your player and then shoot first time.
Unfortunately you cant do bicycle kicks in FIFA 2004.
The throughball button, which is triangle on the PS2, is good for sending balls into space, or past a wrong footed opponent for another player to take without breaking stride. Great for splitting open defences, it depicts who are the true artists in soccer.
Guys, did you know that to change taticks in Fifa 2004 on PC during a match you should hold "C"+"Z" toghather and then a special menu will appear on the down left of the screen... toggel to set your takticks...