Well right now I have my hair dyed blue, and I don't regret it.
I've also dyed it green, red and pink before.
As for tips, I'd say use a good dye, if your hair is anything but blonde, bleach it blonde and then dye it: The colour comes out far better.
Avoid Head & Shoulders shampoo, it washes the dye out far more than anything else.
If it rains, wear a hood: You don't want to end up with streaks on your neck where the dye has come out then the water has dripped down.
OH! And if you get dye on your skin, eye make-up remover works wonders.