Eating less is important, particularly if you know you have a weakness for unhealthy foods (for me it's crisps) but if there's something like that, that you eat quite a lot, just try to cut down on that, and munch on some fruit you like instead.
Drink more water, eat earlier instead of later, and also - if you're busy and don't normally do much exercise, it could benefit you to just go out jogging/running every so often? It doesn't have to be for long, just 15-30 mins would be great, whenever you need a break or something. I've never been very physical, and found that it does make such a difference, even if it's just 15 mins a couple of times a week!