it's not only size that matters; the secret to good form
A small number of reps done in the correct position are much more effective than hundreds of reps done with poor form. Even if you've been exercising for a while and think you know it all you might be surprised to learn that it's not what you do, it's how you do it.
So check out Shane's advice on good form before you start your exercises. This is really important to help prevent injury.