Can I please get some tips before I jailbreak my iPod touch 4g?

Which jailbreaking method is the best? And when I jailbreak it, does cydia just show up? And if I want to unjailbreak it and reset my iPod, will I lose all my music and stuff? And just any other things I should know, I don't want to screw up my new iPod haha! Thanks so much :)