There are 3 types of eggs available from pokestops. 2k, 5k and 10k. You’re only able to hold 9 at a time and they CANNOT be thrown away.
2k eggs have a chance to spawn starter pokemon like Bulbasaur, Charmander, Squirtle, or Pikachu. On one occasion i’ve obtained a Jigglypuff. Since the travel distance required is so little, and the possibility of a starter is very high, they are most valuable. Hatch the 2k eggs as quickly as you can.
5k eggs seem to have a chance to spawn uncommon pokemon like Magnemite, Tentacool, Ponyta, and so on.
I’ve only hatched one 10k egg which contained a very high CP Snorlax. See the bottom of this post for a full list of hatchable pokemon.
A hatched egg will also provide you with about 10 candies of that same species of pokemon (apparently you can get up to 35, i’ve never seen this!)
BEFORE YOU LEAVE THE HOUSE MAKE SURETHE SERVERS ARE ACTIVE OR YOUR EFFORTS WILL BE MERELY FOR YOUR HEALTH.
IF YOU DON’T PLACE YOUR EGG(S) IN AN INCUBATOR NONE OF YOUR STEPS WILL COUNT.
LEAVE THE APP OPEN WHILE YOU WALK OR YOUR STEPS DO NOT COUNT. If you tip your phone on its side it will darken and the PoGo logo will appear. This will help save on battery power but I HIGHLY recommend you set your phone/device screen timeout to at least 10 minutes.
Walking or biking is the most effective way to incubate but that’s not always possible. Driving is an option too but its more dangerous. I only do incubation drives in the middle of the night in a quiet subdivision when everyone’s in bed.
You can’t move faster than 15km/h (approx 10m/h) so doing this in a car impedes the people behind you.
To be effective, try to have more than one incubator going at a time and re-load it immediately after one hatches.
The distance traveled is measured NOT by pedometer/stepmeter but by 60 second delay points measured in a straight line. This means several things;
every 60 seconds your global position is tagged and a straight line is drawn between each tag.
if you exceed 300m in 60 seconds, Niantic assumes you’re in a vehicle and doesn’t count the distance.
if you walk 30 seconds in one direction, turn around and walk back, zero meters are counted.
if you walk 30 seconds in one direction, round a corner and continue for 30 seconds, your distance is measured as-the-crow-flies (a straight line from point A to B as below)
Just because your counter says 2.0/2.0km you still may need a few more meters. This is because the base menu rounds up. To be sure, open the pokemon egg menu and tap the specific egg, it will give you a one hundredth decimal point.
Here is an unofficial list of pokemon and which eggs they hatch from: