Step 1: Turn off your brain, it's just a bug.
Step 2: Stare at the screen until your eyes water.
Step 3: Pretend you're a wizard, wave your wand, and shout "I'm a programmer!"
Substep 3b: If that doesn't work, try Google.
For more advanced bug-catching techniques, visit:
Chapter 4: Magic Trickey Chapter 5: Binary Brewing