Your bracket composition depends on size of your pool. If your pool is on the smaller end (50 or less entries) then it should be a fairly chalky bracket with a few measure upsets. No need to take major chances. With larger pools (100+ entries), you should be taking more upsets but still no need to be reckless. Mimicking the general public with picks will likely not end up different enough to win a pool.
More on the composition of these different pools below the specific brackets.
Methodology:
Methodology: