Actually, I usually do 35 straight up crunches, slowly and making sure my abs bend at both points (people usually just use their top abs when doing fast situps), then I do 35 going to my left and 35 going to my right. My abs are sore as hell after that. Sometimes I use one of the decline benches at the gym for a better range.
Just raising my knees up high in jogging works for my lower abs.
__________________  |