Pokémon FireRed Tips

Fast Experience
A very good place to train is Sevault Canyon. Beat as many people you can, for there is a lot of trainers. Use your VS seeker after you beat them and heal your pokemon. Keep repeating, and your pokemon's experience will increase fast.

Tip: If you have a Pokemon with experience share, go and battle the girl with the Chansey. If your pokemon is a traded pokemon too, then if you beat the Chansey, the experience will be somewhere around 5000!

Rinse and repeat.