I dont think there's any magic bullet. "Best" way is to follow a training program for bicycle racing, be it periodization a la friel, coggan/allen training with power, whatever. Included in any good training program is a mixture of intervals (long and short), structured and "unstructured" group rides, races/training races, and workouts dedicated to skills like cornering.
That being said, I've found that for me, doing short maximal intervals with = recovery (e.g. multiple sets of 10x30"on/30" off, 5' - 10' of 15"on/15"off, 1'on/1'off) is very effective for handling surges (in both rrs and crits). In addition to that, cornering - practice, practice, practice so that you can minimize your effort coming out of a corner. Acclerations out of corner after corner during criteriums really wears folks down, the less effort you have to put out getting back up to speed gives you an advantage. Prehn describes strategy for this in his book (cant think of the name off the top of my head) better than I can communicate.
Good luck - criterium racing is fun and will make you enjoy road races that much more!