Increasing weight
 

How much weight should one add weekly in order to be able to lift more and get bigger? How much is average?

That's a tricky question. The real answer would be however much you can keep progressing with. For some lifters on some lifts it may be as little as one pound a week (Christy Routines) or much much more. I think typical is 5 lbs for small lifts and 10 lbs for big lifts. But those are just guidelines and you need to add whatever works for you.

As road says their is no real answer, it also depends on your routine, an how often is your split an such.

OR makes some very good points. I tell my folks, "one more pound or one more rep!" I am a huge advocate of micro loading once progression stalls. Search for Pace weight, a great investment when you are ready to micro load.

I push for progression when I feel strong. Thus, I'll add a set, more reps, 5-10-20lbs, etc whenever I can.

I am of the opinion that your body progresses in stages, and that you cannot artificially force this progression beyond busting your ass day in and day out. The strength will come, but it will not be linear.

What sort of routine are you following or which routine, if it's a specific routine? Some tend to give guidelines on suggested weight increases.