Abs & Core

Thanks for your replies. I will be doing ab exercises everyday and add 2-3 planks at the end of each ab workout.

Is it really necessary to do 30 secs on / 30 secs off, I find myself going too fast during these 30 secs, can’t feel my abs working because my movements are not controlled.
I have found this 8 minute Ab workout on youtube: http://www.youtube.com/watch?v=sWjTnBmCHTY
Does this workout qualify as low intensity/high reps for endurance?