I hve another question about stretching? I have seen some people stretch just after working a body part, is this correct or should you wait until you're done working out?

I warm-up and stretch in the beginning and end of my work out!

If you have the time, stretching before, during, and after an exercise program can have its advantages. Stretching before exercise can help in the warming up process and it helps to just get in "tune" with your body prior to training.

Stretching during training can help to increase blood flow and remove waste products (lactic acid) which can allow you to recover better between sets. There is also some research on improving muscle size with stretching by creating a greater "space" for a muscle to grow by increasing the size of the muscle fascia. This is somewhat speculative however!

Stretching after exercise help to reduce soreness and allows your body to slowly come back to normal. Basically, stretching just feels good to most people. One word of caution: Don't over-stretch. By this I mean don't push a stretch beyond what you are capable of. You don't want to actually pull a muscle with stretching. It should not be brutally painful when you stretch!

Check out http://www.fitrex.com/fitness_info/exercise528.html