Eat a normal-sized (not the usual restaurant super-sized) meal at meal times, and don't eat anything in between meals. When you have a meal, wash it down with water. Avoid any drink that has any kind of sugar in it, including fruit juices - or else you're only adding unnecessary calories that you will have to burn off later on. Have a glass of wine with a meal if you want to, but avoid any heavier drinking. The alcohol is the same as sugar.
That's pretty much all you have to do. If you're riding, don't count on riding alone, because it simply will not burn enough calories if you don't limit your intake. Even if it does because you're going for long rides, chances are that the burned calories are easily negated by post-ride hunger anyway.