These aren't really glitches, but rather two things the computer does when you perform a certain action. These will assist you in defeating the computer.
Please Note: These only work on the arcade version as far as I know. I don't know whether they work on any other version of the game. Also, they will only work against the normal characters--that is, anyone but Shao Kahn and Motaro.
The first "glitch" is if you jump back and hit an attack button while you're in the air, the computer character will automatically throw his/her projectile. This will leave him/her vulnerable to an attack. Note: You must have the control stick in a neutral position, or it won't work. You must tap the direction rather than hold it.
The second is if you knock the other character to the ground then perform a sweep (back + LK), the computer character will jump back. This will allow you to throw your projectile and, if you are quick enough, hit him/her with it. At the very least you will be out of harm's way.
The best characters to take advantage of these glitches are Scorpion, CyberSmoke, and Human Smoke, since they have the best attacks for use of the first glitch (a teleport) and for the second one (the spear). If you knock your opponent down, you can just keep spearing him/her and knocking him/her down.
The best thing to do against this brute is to let him advance toward you, then jump straight up before he gets to striking distance (he'll keep coming) and unleash your best combo. Repeat the process, jumping or blocking his fireballs and keeping a safe distance (but not too far) from him.
Another strategy is to use Human Smoke or Scorpion, and, when you've landed a combo, immediately teleport. He'll block it, then punch at you but miss, leaving him vulnerable to another combo. Repeat the process until he doesn't block the teleport or until he blocks the end of the combo.
Again, the best strategy involves Scorpion and Human Smoke. As with Motaro, he will block a teleport and try to hit you but miss. Unfortunately, his punch sometimes connects (though the hammer and kick won't) so it's a little more dangerous...but then again, this guy is always dangerous! If he doesn't block the teleport, just spear him and proceed to throw your combo.
Another character you can use is Cyrax. For some reason, the big guy never blocks his Green Net, so just use that over and over again.