I just bought a 1996 Taurus GL, and apparently the brakes don't work every time I brake. What can it be? What should I do? How should I check to see what it is?

You probably mean the brake lights don't work, eh? Could be that all the bulbs are blown, could be a fuse or it could be the switch on the brake pedal. Check 'em out one by one. If it is an intermittent problem check the switch first.