When do you think I should move up in the amount of weight I'm lifting?
When you feel still energetic after a set of 8-10 reps. Then you try to do like 15-18 reps and feel still fairly easy. Now you should bump up the weight.
Now everyone's body responds differently, so some people may just bump up the weight and do like 4-6 rep per set, then work up to the 8-12 rep per set.