depends, if you want to lose weight then Before
if you want to bulk up, do cardio on a diffrent day.
heres a link with more info:http://weighttraining.about.com/od/techniquesandstrategies/a/cardio_weights.htm
I just do a 10-15 minute cardio before work outs to warm up and get my heart rate up.
recently trying this new routine for my upper body
after doing bicep curls, I go STRAIGHT into pullups or dumbbell rows, by doing that, my heart rate won't drop and my muscles will still be working out while the secondary muscles are "resting" but still working out albeit with a lighter load
so the new routine im trying out for total upper body is Bicep curls/pull ups or dumbbell rows then Pushups or chest press/Kick Backs or Skull Crushers, if my arms aren't dead yet.
lower body, i just do all the machines in a circuit. i think biking with 24oz denim to the gym is enough of a work out already for my legs lol