My trainer has me do treadmill (fast walking) for 30 mins, do 3 sets of weights (circuit) and then another 30 mins on treadmill. If time is a factor, I can lower the amounts on the treadmill, tho. This is an active warmup and cooldown and seems to cover the basis of 'before or after'
I have done the empty stomach and not empty. Not sure which is better, but am going to do the empty stomach for a while and see how it goes!

Nicole