I suppose it's just training yourself to make the right choices when it comes to ordering room service, or if you eat out, choosing the healthier options.
If you're a meat eater you could perhaps order grilled chicken and a salad for example rather than order a burger and chips. Depending on the standard of hotels you have to stay in, you could ask them to make some adjustments on meals from the hotels restaurant menu. Or if you are going out to eat, order things that don't have creamy sauces or ask for dressings to be put on the side, order from the starters menu so you are having smaller portions.
Keep plenty of water in your room to drink. If you are able to have alcoholic beverages of an evening, perhaps cut back or cut those out to save on consuming empty calories.