Crunches are one of my favorite abs exercises. I find them easy to do, effective and variable; since there are many types of crunches. E.G, I do crunches while liftig weights, to rest the arm for a bit while training another part of the body. And I love putting them into abs workouts! The most important is the right teqnicue; and you’ll find that crunches are easier than traditional situps. That’s mainly because you don’t crunch up as far as with situps, and therefore you don’t get that neck-pulling problems many get while doing situps.
I post a video for technique on regular crunches, which is one of them that I relay on. Vary the crunch sets by doing reverse crunches, bicycle crunches or side crunches!