To safely and properly "fix" a squib load situation, first pay attention when you're shooting! As soon as you noticed any difference in the sound or feel of a shot, stop. Unload the firearm. Then disassemble it, if possible, and examine the barrel by looking through it (for a revolver, drop a weighted string through the forcing cone and see if it comes through the muzzle). If there's an obstruction, take a properly sized wooden dowel (it should be close to the diameter of the bore, but should move freely in the barrel), and place it through the muzzle or chamber end to determine where the stuck projectile is located in the bore. Then, take the dowel through the end of the barrel that's furthest from the projectile, and gently tap the bullet out from the closest end of the barrel to it.
Even rarer, but potentially more dangerous if proper safety rules aren't observed, is the "hangfire." A hangfire is defined as a delay in the detonation of the propellant (gunpowder), which in turn results in a delay in the firing of the cartridge. The delay can be as long as seconds, but is often almost undetectable. It's evidenced by a "click," instead of a bang, but can also occur when you hear a much-lighter-than-normal sound upon on the firing of your handgun. Like squib loads, hangfires are often blamed on sloppy reloading habits, but can occur amongst any type of ammunition, including factory manufactured rounds.