Lighter weight and many reps always worked for me - I wasn't about to enter a weightlifting contest (and I didn't want to risk musculo-skeletal damage that would come back to kick me in later life).
heavy weights and low reps vs light weight and many reps?
The old approach used to be to first build the muscles that you wish to refine.
I would assume that is still a good approach.
Nevertheless, here's two sites you may wish to visit:
http://www.bodybuilding.com/fun/high-reps-low-reps-which-rep-scheme-is-best.html
www.shape.com/celebrities/star-trainers/ask-celebrity-traine
