Hey Yasmin,
I'm in the strength building phase of my training cycle. So I'm back in the gym pushing heavy weights for a couple of months. Because I'm really really pushing myself right now and my muscles are sore I add extra protein to my diet. Right after my workouts I take on a small amount of carbos to replenish glycogen stores in my muscles and liver. For the next meal I add a bit more protein to help the muscles heal and get stronger...maybe a another ounce or so of chicken or tofu at dinner.... or I make a smoothy with added soy protein.
I'm not really sure about how much "extra" protein I need at this time. I just go by how I feel and how well I'm progressing in the gym. Be sure to have some measure in mind for how you will register any gains you get from supplements. I go both by gains in strength (I record what I can do at each weight lifting session) and how well I recover between sessions.
When thinking about how much "extra" protein to include in your diet remember that your body doesn't store amino acids (the stuff proteins are made of). So any protein your body doesn't need gets eliminated and your kidneys get an extra workout!
-traveller
"It never gets easier, you just go faster." -- Greg LeMond