How do I prevent an egg cracking while hard boiling it?
I used the method here before with good success: http://simplyrecipes.com/recipes/how_to_make_perfect_hard_boiled_eggs/
Basically you start with the eggs in the pan with cold water and bring the water to temperature, right when it reaches boiling you pull the heat back and let the eggs cook for 10 minutes.
You don't need a full on boil to hard boil the eggs.
In my experience, steeping for 8 minutes is plenty and tends to reduce the greening of the yolks. That also gives you a buffer if it takes a bit of time to get back to the stove or fumble for a minute to prepare the water bath.
This above method is how I hard boil eggs. It does a few things. First, it lets you put the eggs in the pan carefully so they don't crack from that. Second, you are not shocking the eggshell nor causing sudden expansion off the inside of the eggs (IOW making the inside bigger than the outside). The cooking is more gentle so the egg is cooked more evenly. I bathe my freshly boiled eggs in ice water for an hour to halt cooking sooner. It helps keep the eggs from getting tough, and it also Aids in shelling the eggs because the sudden chill makes the egg white sluff off the membrane.
Now, if you are going to make tea eggs or iron eggs which is to start boiling the eggs a second time in a spiced tea of sorts, you want to do that mostly right away. If you refrigerate your eggs over night then use them for tea eggs, they tend to expand grotesquely.