2 small debugging tips

Here's 2 small debugging tips :
- understand the code you're trying to fix.
Debugging code written by somebody else sucks but it's very important to grok the code before debugging it. Only when you understand the problem you should attempt to fix it.

- be well rested and have a clear head.
This is very important. If you're tired you might spend a lot of time trying to fix something only to find out that it took you 5 min the second day when you were well rested.