Eat every 3 hours. Even if it's something small. One of the biggest culprits for psychological cravings is falling blood sugar levels. If you keep your levels steady, you simply won't crave the same things. The easiest way to combat cravings is to avoid them in the first place.
Drink water. Dehydration confuses the body and will often make it feel hungry, especially if it's cool out. A small glass of water each hour will keep your stomach full and keep you hydrated.
Wait. Real cravings stay with you but psychological ones don't. If you've eaten enough and are hydrated, putting off a decision for 15 to 20 minutes will help the craving dissipate.
Distract yourself. Along the same lines, if you start doing something else the feeling will usually pass. If you've been working in front of a computer but feel the need to eat, do something else. Make a phone call or read the news. Changing your mindset might be all you need.
Exercise. If you start to exercise and your cravings aren't physiological, you'll feel better almost instantly. If they are physical, you'll never be able to really get into your workout, which is a sign that you need to eat.
Challenge your craving. Some people like to attack things, and so prefer the approach that is "Go ahead and take your best shot. I don't need food and I'm not eating!"
Keep healthy snacks around. Sometimes you just can't take it, especially if you're on a restricted-calorie diet. Keeping healthy snacks around will help. Have a piece of fruit or some raw veggies. If that doesn't help, you'll know your craving is psychological.
Change your routine. Habit can affect a craving, so shake up what you do, even if it's just slightly. Turn off the lights in your kitchen and try not to use that room. Change the lighting of your house, move your desk, sit differently, get up every so often and stretch, or drink waterdo anything different. Forcing simple changes can make it easier to follow through with tougher ones.