There are enough Pokémon Go hacks out there to fast-track you to becoming a Pokémon Master -- just don't think it'll be all Sunny Days and Ho-Ohs once you hit level 30. But on your way there, you're bound to be walking a lot. And that means hatching eggs.
Do not hatch eggs without considering these two points first.
Wait to hatch 10km eggs
Since they seldom fall into your lap, don't go wasting your good eggs and the rarest Pokémon by hatching them when your XP is low. Wait until you've leveled up a while, THEN hatch that Snorlax. And for kicks, here's a Pokédex somebody put together to show you which Pokémon hatch from which eggs.