95% of everybody i've seen or read about typically uses the 'pyramid' system where they are increasing weight after each set.
I was originally trained to reduce weight after each set (start out at your max for reps) in order to maintain a target rep range (say 8-11 on lighter days, 4-7 on heavier). Obviously if you're increasing weight, you reps are going to diminish.
For the past month I have switched to the pyramid system just to change things up and keep it fresh, but would love to hear your opinions on this.