I always spin my wheels before a ride like others have mentioned.

I always check my brakes by going through a little pre-ride routine.

Stand beside the bike and roll it forward slowly (only a few inches are needed) then apply the front brake, the rear wheel should lift without having to squeeze the lever too hard. Roll the bike backwards and apply the back brake. The front wheel should lift off the ground without having to squeeze the lever too hard. There should also be plenty of room between the lever and handlebar when the wheels raise. I also always check the brakes when I start riding, before I need them, just looping around the parking lot or whatever and making sure they feel right.