One frustrating aspect of making enchiladas is the propensity of the tortilla shells to crack when you begin to roll them. Corn tortillas dry out easily, so it's best to use them when they're at their freshest and store them in a firmly sealed plastic bag with the air removed. The shells may still fall apart on you, unless you know the simple trick to keep a corn tortilla from cracking up.
Steam Them First
A dry corn tortilla needs moisture to keep from cracking. The simplest way to put moisture back into a tortilla shell is to steam it until it's pliable enough for rolling. And one of the simplest ways to steam a tortilla is to place it in a steamer basket over a pot with boiling water in it. Make sure the bottom of the steamer basket isn't touching the bubbling water. The shell should steam for about 15 to 30 seconds.
Microwave Steaming
If you don't have a steamer basket or want to wait for water to boil, you can steam the tortillas in a microwave. Run the shells under hot tap water and place a small stack of them on a plate. Cover the shells with a wet paper towel and microwave for 30 to 45 seconds. Let stand for at least a minute before rolling.