I would recommend eating a balanced diet - not too much protein, not too much carbs, not too much fat. A little bit of everything, with a good variety of seasonal vegetables.
It's important that you enjoy the food you're eating, and that you eat when you're hungry - not just arbitrarily because you 'need' to get the calories.
In the past I used to log all the food I consumed on FitDay.com, pursuing an optimum diet that satisfied my daily nutritional requirements. This included counting calories, to the extent that I would stuff my face with additional food even if I wasn't hungry to ensure that I consumed the 'correct' amount of calories.
These days, I'm far more laid back about the whole thing. nutrition logging sites such as FitDay.com are very useful, however they can also be a little damaging, especially if you get too hung-up on every nutritional detail. Again, food is meant to be enjoyed - if you don't enjoy it, your body will not receive its nutritional benefit.
Finally, please remember the of the wise phrase 'You are what you eat'. Actually, a more accurate version would be 'You are what you digest' - meaning, it doesn't matter how many calories you put into your body if the food is not being properly digested and absorbed. My digestion and absorption aren't great (I'm also perhaps a little underweight for my height), however I believe things are steadily improving.