Well normally people do the whole bulk/cut deal. But I was fairly inexperienced, and that actually allowed me to go through with it without doing the cut/bulk cycles and just putting on straight muscle.
As far as my diet, it was essentially the same as it was before. When I first started I wasn't drinking soda but that was as much dietary restrictions I put on myself(other than being a vegetarian of course
) that I can think of. I was a high school kid who didn't really know how to cook(now I can a little, but am too lazy most of the time) and my workout schedule was designed in such a way that I never ate dinner with my parents anymore. I am actually eating the same kind of stuff I was eating before, and the big major difference is that now I am getting a 70g of protein, 700 calorie soy milk+soy protein shake post workout along with the other stuff I ate(almost all of it was lean cuisine pizza, amy's meals, or some sort of stir fry). So I was getting around 1g per lb, and I still am. Um I have a fairly high metabolism and when I started I was running every leg day. I have since intensified my workouts greatly, so the cardio aspect isn't really needed to keep my body in check since I burn a TON of calories lifting as much as I do. I still definitely indulged myself in some of my favorite(chips and dip and so forth), but its one thing for a person who is skinny to be doing that versus someone who doesn't have as low a body fat to start out with.
Just to make sure you picked it up, I do NOT think of myself as a dietary expert in any sense, and am probably even less knowledgeable than you. I have gained a lot of knowledge about fitness in this process, but because of my metabolism I really didn't need to do a whole lot more than just "eating more."