If you have a Pokemon with the Magma Armor or Flame Body ability in your party, it will cut the hatch time in half.
If you have a Pokemon egg and are waiting for it to hatch, it will hatch after 10,250 steps. The best place to get a lot of steps is in Amity Square. By doing this, you are able to collect something from the Pokemon that you are walking after every 200 steps.
In Solaceon Town, get on the far right side of the path next to the Pokecenter. Then, ride your bike in the fastest gear up and down until you hit a tree or mountain and repeat. You must have done at least 400 steps each "lap" to get an egg to hatch more quickly.