You want to minimize movement as much as possible. Your left hand is going to be sitting around the WASD most of the time. These keys correspond to the basic movement directions, and occupy a lot of the key presses in a game like WoW. Other keys immediately around the WASD keys are Q E R F Tab ~ 1 2 3 4.
So, let's look at what are some good things to put on each of these other keys:
Q and E strafe left and right, respectively. This is a good thing to leave as is.
The R key is automatically used to reply to people that send you a tell. This is nice in social situations, but not very necessary for raids or game play situations. In my key maps, I often have this mapped to shield block if I'm tanking, or to assist the main assist / main tank if I'm in a DPS role.
The F key is automatically used to assist your current target; or to put it another way, to select the "target of target." This is very very useful for healing and pulling mobs off other people.
The Tab should keep it's default behavior, which is to target the next closest enemy.
The ~ key is nice to use for whatever function you need to press in the middle of a fight. As a tank and someone who often has to mark mobs and lead groups through instances, I use this to trigger my microphone on Vent. I can hold the ~ key down and spam shield block at the same time while tanking and asking the healers to readjust, which is a very useful thing to be able to do.
The 1 2 3 4 keys are defaulted to the first four button on your main action bar. It's a good idea to look at what the most used in-fight abilities are for your class and map them to these locations. Here's a big hint: it's not your "start attacking" command. You only use that once per fight, but you probably use Arcane Shot a lot more. Try making your start attack command be on a "far away" key like = or -. You'll find that all of the sudden you're doing less hand movement during fights.
On the G15 and keyboards like it, there are 18 programmable keys on the left side. These keys are very nice to be able to put macros and key press assignments. For instance, I have one that charges a mob and switches to defensive stance, and then executes a shield slam. I do this using the G15 software, not anything by Blizzard. These keys are less comfortable for the left hand to go to and find easily, so they should be used for "one shot" actions that don't need to be done very often, and not in the heat of battle (ie: /wave).
To wrap everything up, the name of the game in effective keyboard game play is to minimize the movements of your fingers. You don't want to have to reach across the keyboard and find a key to press that does an important action. If you miss, you might wipe the raid at worst, or make the wrong move at best.
What are some tips that you have to maximize your keyboard game play?