Three tips for starters.
1: Put down the fucking camera.
Arm length photos are stupid. They put your face at bizarre angles and are more likely to be blurry from hand motion. Most cameras, both film and digital, have a timer on them. Use it. Love it. It will allow you to stand more naturally and gives you greater room for positioning error, all while reducing blur.
2: The flash is your enemy, not your friend.
Most on-camera flashes suck. Largely they are unused by professional photographers. They suck the color out of you at best, and at worst they copmpletely obliterate all that lovely definition you've been working on by lighting up all your muscular nooks and crannies with a floodlight. Directional light is your friend. Take a couple pics in different places under and overhead light or with a gooseneck lamp pointed at your side, watch how those abs no one can see in your photos suddenly pop out! WOW!
3: Angles angles angles!
Do not, do not, do NOT stand absolutely square to the camera. Do something to set off the angles. Turn a little, twist your hips, do a half profile, whatever. Standing square to the camera gives the viewer a look exactly at all your widest points. It accentuates how your body droops rather than how your body looks being dynamic. Like someone above mentioned, you want photos of your muscles in motion. Twists and bends accomplish this.
Oh, and one more 'cause I'm feeling generous.
DO NOT PUFF UP YOUR CHEST. EXHALE when you take your photos. Inhaling causes loss of definition through your entire torso and lifts your shoulders, removing your neck and narrowing your profile. Exhale.