Anything other than crap. i.e. as you say chicken, tuna, pasta, rice etc. All good natural foods.
Stick with this pretty simple formula;
1.5grams of protein per pound of bodyweight daily.
2-3grams of carbs per pound of bodyweight daily.
Stay away from unhealthy saturated fats, and stick with healthy. As long as you're getting enough protein from chicken, tuna, eggs etc, you should'nt need to worry.
And down the gym, stick with the basics;
Rest
Always give your body enough time to rest and recuperate from your hard workouts, and never underestimate the power of recovery. Many bodybuilders who train four days a week prefere to rest completely on Wednesday and over the weekend. Others train every other dayso that they do not have to train two days in a row. Both systems are good.
Training
You should never, ever, train for more than one hour and fifteen minutes, because if you do you will simply be defeating the whole purpose of building huge muscular mass.
Your workouts should consist primarily of heavy basic compound movements which stimulate the larger muscles of the body. As far as sets and reps are concerned, I would recommend one or two sets of 8-12 reps as a warm-up followed by one really hard set of 8-10reps, almost to failure.
You should also try to increase your training poundages over a certain period of time because regular strength increases muscular growth. Also, when you're training try your best to concentrate on the lowering part of each movement. This is known as the negative part of the exercise, while the actual lifting of the weight is called the positive. Negative reps are just as important (or even more important) than positive reps, so lower the weight slowly at all times, and never allow gravity to take over.
Contraction is another very important aspect of successful bodybuilding. When you press or curl the weight to the contracted position, try to squeeze the working muscle for a second or two.
This is only the very basics, just stick around and read up on as much as you can.