Me and Smith discovered this tactic that 90% of the time works 100% of the time! First you should practice in a custom game though.
Instructions:
When someone points a charge up shot at you and your close enough that it probaly wont miss, jump before they fire it. Do not jump toward them because it will hit you alot easier. Now when your at the peak of the jump wait about a split second til you start falling, then click down on the crouch button to fall really fast, fast enough that the plasma shot will go over your head. If you click at the peak of the jump you will hang there a second and hover so you have to wait until your falling to crouch.
Now the real test is to do this while your stafing and shooting and the other guy is moving and stuff, but it really does help.
If anyone else has any gameplay tricks post them in a new thread with a similar title as this threads so we can maintain some organization and I will sticky it so it stays at the top of our forum, or Titusfied will.