Avoid saturated fats in your food where possible - normal fats are a lot easier for your body to break down, whereas the saturates (e.g. junk food) can also raise your cholesterol level.
Just stay healthy mate. Avoid steroids - have a look for some of the pictures of Sylvester Stallone after he'd finished Rocky. I remember seeing them years ago; he came off the steroids he'd used tobulk up for the role and had badly deflated, so much so that his chest was almost inverted!
Like the guys said, don't overwork your muscles - work on different groups of muscles each visit, working in a cycle til you get back to the first set. Don't forget to have a protein shake after your workout too - this is when the body will be gasping for more protein. Remember, the body first uses protein to repair the muscles, only then (if there's enough) will it use the protein to build.
Might be worth getting a personal trainer for a session once a week, someone who is qualified would really be able to help you towards your goals faster.