actually i'd beg to differ with that "we can't pick and choose" philosophy. that would be implying that only the "rich and famous" were given bodies to do so?? i don't think so.. yes, overall work outs and eating properly, etc. are the keys to start with. but one thing i was shown that i enjoy way more than crunches are "leg lifts". lay on your back (preferably on a mat or towel for something between you and a hard floor!) and lift the lower half of your body up. when lowering don't go all the way down to the floor, it will work the ab and stomach muscles. also once you get into doing them regularly, add a ball of some kind- a plastic one, or basketball/soccerball the larger the size, the more of a challenge.. in between your ankles/shins and do the same lifts with the ball.
this has helped me anyhow, and it doesn't bother my lower back. good luck.