As others have suggested, using dharma dyes would be a good choice, they also make kits if you want/need guidance. Follow the directions and you should have good results. Dharma is great but the shipping can be expensive. This kit by jacquard is available at several retailers. I also hear that grateful dyes has a kit, but I am unfamiliar with that one myself. All of these should produce nice vibrant colors.

(For regular laundry washing) Even the best dyes will fade some as the shirt gets wear and tear, just the same as any clothing does. To keep you tie dyes as bright as possible for as long as possible, washing the shirt in cool water, inside out and with soft, non abrasive fabrics (such as jeans and towels) will prolong the life of your shirt and the bright colors overall.