Make sure, when you're doing crunches, to actually crunch. Try and get your ribs to squeeze towards your mid-section. Like everyone else has been saying, use your abs to lift, not your throat. When working out, just focus on your abs and it should come naturally. If you're doing a lot of sit ups, make sure to stay focused and not just get into the motion. I don't know what you mean by lower ab workouts, because those include exercises like leg lifts. Leg lifts shouldn't hurt your neck as you should typically lie flat.