Reps vs pounds in weight training

What is the best approach to use with weights when not aiming to bulk up but looking to drop pounds? I know I should be stressing the number of reps rather than the weight, but how many reps is best? Fifteen, 20, 25 or 30, or what?

iVillage Total Health seems to says the it doesn't matter much whether you do many reps with few pounds, or fewer reps with more pounds. Burning calories is all that counts.

One poster at Peer Trainer had this to offer:

The studies the referenced could both be true, and I believe that they are. Here's what I've learned through years of internet search and research, confirmed by a number of other people with similar backgrounds (i.e. we don't claim to be experts, but have done a good deal of work looking into these things):

To build tone without bulk, lift what you can do 3 sets of 12 reps with. You should be worn out at the end, and unable to do a 4th set. That's how heavy a weight you should use.

To build more muscle mass, do the same, but with enough weight that you can do 3 sets of 6 or 8. So, heavier weights for less reps.

Light weights with more reps does not mean lifting a 2lb weight 40 times in a row, and not being all that tired in the end. You should be getting a good, hard workout either way. Your muscles should be tired afterwards. You should need to stretch well afterwards. When you first start a program, you should be sore the day after. If you aren't working hard, you're essentially wasting your time.

Sounds like a plan to me.

Ride 30 mins stationary bike, Weights 20 mins