This is a very common question, and to be honest, with all of the research I have done and numerous trainers and nutritionists that I have spoken too, it seems like there is no 'perfect' amount of protein that you should consume.
From what I know myself and have found out, it seems that anywhere from 1-2g per lb body weight is enough. But there's a problem, and that is the fact everyone is different so is their protein needs and absorption rates. Some guys find that packing on muscle is quite easy, whereas others find it very hard, so they need more of everything including protein.
In simple terms, if you want to gain muscle and get big, then you need to eat more. If you want to lose weight, you eat less right? well its the opposite to get big. Everyone knows the role of protein within the body, so if you want to add muscle mass, then you need more of it, but you will have to experiment yourself with how much YOU need. Just because one trainer says 'You need 1.2g protein per lb body weight', does NOT mean that if you follow that instruction, you will become 'hench'.
As with anything, find your own limits and needs. In the gym, everyone has their limits, and everyone is different, it is exactly the same when it comes to nutrition. The nutrition side of muscle building is pretty much 'recovery'. You're trying to repair, recover your body to get stronger and ready for the next workout. I personally noticed a difference when upping my protein intake and eating more in general. Before I used to feel like I needed 2-3 days to recover, but after upping my nutrition, I felt find after just 1 day rest!
Play about with your nutrition until you find what works for you. But as mentioned, it seems to be between 1-2g protein per lb body weight. Obviously depends on your goals as well - if you just want a bit of muscle, you don't need to eat like a horse! but if you want to get big and muscular, then you obviously need more food!