1)Don't even buy any snack products when you go shopping. Do not even go down the aisle with the biscuits on it, or the crisps one, or the chocolate one, or the ice cream one. If you don't even look then you wont buy. If you must have some sort of snack in the house, go for a non-sugered cereal. Regular Shreddies (not frosted honey or coco), or bran flakes, and nibble on those.
2)Always have a pint of water on the desk. Keep it topped up. Drink some when you get pangs. You'll have to run for a pee more often, but it helps keep you full. When you have a drink of water and it doesn't kill hunger pangs then obviously, eat something.
3)Bananas. I say bananas because they're awesome, but you can [insert your favourite fruit here]. Grapes are super sugary though so maybe not those, and do not go for dried fruits that aren't apricots because almost all of those have some sort of sugar or honey added. Bananas are awesome. And if they get a bit black for your liking. Make some banana loaf using a recipe which doesn't involve 400grams of sugar per tin.
4) Get a good nights sleep every night. If you get less sleep, you're awake for longer and your body will send you more hungry signals, and because its late, you'll want to snack. Get your 8 hours a night, no staying up till 4am working/playing Civ/browsing Head-Fi.
5)Eat a high fibre breakfast. All Bran is pretty manky, but bran flakes, Weetabix, or if you're a little bit of a philistine, Shredded Wheat are all high fibre and healthy. Fibre keeps stuff firing through you properly. Getting clogged up makes you feel horrid and can lead to weight gain as well.
6)Cut the booze right out, or at least, cut it right down if you drink a lot. Alcohol (plus mixers) contains vast amounts of calories and once you've had a few drinks you'll get the nibbles and want crisps or peanuts. Once you've had a few more you'll want as big giant chippy or a curry. Then there's the cooked breakfasts which so often help with a hangover on top of it all.
All good tips for keeping the paunch off or losing a bit of weight.