Hotel's generally have some sort of continental breakfast. Get some oatmeal, toss in some cinnamon and some packets of splenda (get it from the sugar packets for coffee), and some milk.
Lunch salads with oil and vinegar on the side are good. A chef's salad or some sort of grilled chicken salad are both good choices. Just make sure to ask for a smaller portion of cheese and the dressing on the side.
Dinner is similar. As others have said, grilled salmon or chicken is good, along with some steamed veggies. Stay away from the bread and the potatoes.
Don't be afraid to add musclemilk to your days for some extra calories in a pinch. It's portable and convenient.
Lastly, don't feel like you have to finish everything on your plate.