I wouldn't call the first exercises, so much as two bass lines I feel are good to warm up with. The intro to Deja-Vu and the bridge/verse of Revelations, both Iron Maiden songs.
One I use a lot I picked up from Alex Webster's book, something along the lines of this:
G-------------------------------------
D-------------------------------------
A-------------------------------------
E-------------------------------------
B--5-5-5-5-7-7-7-7-6-6-6-6-8-8-8-8--
Just a straight pattern of 16th notes, works absolute wonders for getting a feeling of 4 beats using 3 fingers. You could slow it down or speed it up as you like as well, if you find any inconsistency in the pattern or are just starting it up. Really gets easy to do, so you can focus on hearing 4 beats without actually stopping to mentally count them.