What can I do to prepare for a marathon?

I am 25 years old, the last marathon I did was in 1993. What kind of trainig should I do? Should I change my diet?|||Just do loads of jogging. Start with something comfortable (1 mile?) and build up your distance every day. Eat lots of fruit and vegatables and not too much fatty stuff!|||practice ur endurace..exercise more..make sure ur muscles can take such an intense change|||You have to train more harder.|||start with short runs, and work your way up to the marathon. Drink plenty of liquids,and eat a banana...also stretch before running|||no, i think you should stretch and get plenty of carbs. do not work out before the meet.