The trick is to think MULTIPLES OF FOUR. If you play the game so that after your turn, a total of 4, 8, 12, 16, or 20 rods have been removed, then you are guaranteed to win.

The only exception to this is if you go first. If that happens, just pick any number of rods, mentally add those to the number that your opponent picks, and then when it is your turn again just be sure you keep the overall total removed a multiple of four.

Try it. You won't be able to lose!