How to missthreat your abs:

warm up!

30 straight leg lifts
50 crunches where you knee on the flor and bench (hold on to a strechband or sth.)
30 bulks, where your knees or toes are on a fixed underground and the rest is on a smooth floor, then you take a towel or sth and put it under your ellbows. Voilà time to crunch deep in your muscles
and to relax 25 normal cruches..

Have fun.. dont forgett to stretch :)