first you must be sure your master cyl is good, and all shoes and brakes are in good condition, and adjusted properly.
you can buy "line locks" which pinch shut each of the three hoses to help isolate the problem.
if you pinch all three shut, and the pedal is good, the problem is at the wheels. if the pedal is still sloppy, it usually will be a bad master cyl, or pushrod adjustment, but you should always check the condition and adjustment of the shoes and brakes anyway.
never look for an "easy fix" when it comes to your brakes. buy a service manual. when in doubt, take it to a qualified mechanic.