Eating habits
Right, first things first think protein. Try to make sure you eat as much protein rich foods as you can. Tuna and eggs are both good, though don't overdo it on the eggs because they're high in cholesterol(2-3 per day max).
Make sure you get 3 meals a day. Some people prefer 4 or even more, but as long as your protein and calorie intake are sufficient it doesn't matter.
For your biggest meal try to include plenty of:
Lean steak (and cut the fat off!)
Chicken
Fish (all types)
Turkey (the lowest fat, highest protein meat)
Basically, look on the packaging and find foods with more protein content than fat. Ideally your meal will be 50% protein, 30-35%carbs and 15-20% fat. Don't cut fat out entirely, non-saturated fats are actually good for you, just moderate your intake. Some cheeses are ok, but not too much because it's very fatty. For snacking, things like peanuts (or any nuts), sardines(if you can stomach them!) are ideal.
The average daily intake for an adult man is 60g protein, so you ideally want to exceed this. Aim for about 100-130g, but don't worry if you have to use supplements to make up this amount.
Supplements are a good way to up your daily protein intake. 'Whey protein' is probably the best powder, and some protein bars actually taste pretty good, as well as containing 30g protein on average.
Also, multivitamins are a good idea, because it's very difficult to eat a lot of fruit and veg whilst keeping up this kind of diet.
Note: The info above is assuming you want to put on lean mass. Of course if you are slimming or training for endurance sports, you will probably want to disregard this post!
Hope this helps
Paul.
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