I find that eggs are good. A nice big omelette to soak up the crud left in my stomach, and to give me some energy to get started on the day.

However, most of my hangovers are dehydration-caused. A nice big 2 pint glass of cool blackcurrant squash usually helps with that. Drink it slowly, or you'll just get bloated.

The most reliable solution however, is to drink plenty of water before going to bed. If you wake up with a headache, drink some more water, take a painkiller, and then go back to sleep for another hour.

Alternatively, read this