Over time you get a feel for the tension and direction to pull the white tab successfully. Initially I tore them all the time, now I never do.
As mentioned above, the first few shots in the pack are the worst. It does help to remove the springs. You can also cheat and open the back slightly BEFORE you pull the white tab. Pull the tab enough to get it started (less than 1/2 inch) and then close the back again. Now pull the white tab fully, it should be easy now.
Lastly, it's pretty to easy to recover from a torn tab. Open the back slightly, reach in and grab the remained of the torn tab, and give it an initial pull, as above. Once it is started, close the back and keep pulling.