There are a few methods for cracking eggs including; cracking on a flat surface, cracking on the edge of a bowl, or using one hand. None are right or wrong. Below I will cover the different methods, but do what works best for you and let me know which method you like best!
Step 1: Methods
You will always want to crack the egg around the wide center where the shell is the weakest. The goal is to not allow any eggshell pieces to crack off and get into the egg!
Cracking on a Flat Surface
To crack an egg on a flat surface hold the egg firmly in one hand. Expose the widest (and weakest) part of the egg and hit it hard enough on the countertop to make a large crack. Press each of your thumbs into the dented crack and pull the two halves of egg shell apart. The egg inside will easily fall out...preferably into a bowl! I like to crack eggs near a garbage can so the shells can be easily and cleanly disposed of.
Cracking on the Edge of a Bowl
This method is done exactly as above, however, you hit the egg shell on the edge of a bowl instead of a flat surface. Unless you have a heavy bowl you will need to be holding the bowl securely with one hand while cracking with the other. Otherwise it will just tip over! This method produces a larger/wider crack that's easier to open.
Cracking with One Hand
This is by far the most difficult method but if you can learn to do it, it makes cracking eggs faster and leaves one hand completely mess free! Hold the egg in one hand and hit it on the side of a thin bowl. Hard enough to crack the egg shell almost half way through. With the thumb and pointer finger holding one half of the shell and the three remaining fingers holding the other half of the shell, pry the shell open and free the egg!