My code isn't working. Blah!
The very first thing I do is read through the code. More than half the time, I'll find the bug, just by reading the code.
This only works if I actually pay attention. I don't just let my eyes wander over it, saying to myself, "Oh, yeah, I recognize that." Recognizing isn't enough.
I check each computation, check that the right variables are used, run through what each
If does, what code is run, and what is not.
Sometimes, my attention wanders. That's normal for humans. I don't beat myself up over it, just bring my attention back to the code.