"Dehydration is responsible for most of the nastier effects of a hangover. Alcohol is a diuretic, which means it speeds the loss of water from the body - causing parched-mouth thirst, headaches and that feeling of continual dizziness. Nausea, vomiting and indigestion are caused by alcohol irritating the stomach lining, and can add to the dehydration."
"Before you go out, eat a good meal. On this occasion only, a fatty one is beneficial as fat is digested slowly and will protect the stomach from the irritating effects of alcohol. A glass of milk also protects the stomach and slows the absorption of alcohol.
While you're out, alternating water or non-fizzy soft drinks with alcoholic ones limits the amount of alcohol you consume. Avoid fizzy drinks as they increase the amount of alcohol getting into the bloodstream."
"Before you go to bed, drink at least a pint of water and some orange juice - vitamin C speeds up the metabolism of alcohol by the liver. Eat some toast, too - a lack of sugar is responsible for that wobbly, trembling feeling and it will help to settle your stomach. A sports drink is a convenient alternative."
"It's best to plan ahead and have a few things close to hand. If you're feeling queasy, antacid liquid or tablets will settle your stomach, as will a cup of ginger tea. Ibuprofen or paracetamol will relieve your headache. Anti-sickness tablets may come in handy.
Once again, water, vitamin C (fruit juice or tablets) and toast are the best things to consume. Eggs are also good as they're packed with cysteine, which is said to mop up the destructive chemicals that build up in the liver when it's metabolising alcohol. This probably explains why a hearty English breakfast does the job - if you can face it."
http://www.bbc.co.uk/health/conditions/hangover1.shtml