Don't see the top comments mentioning that, so I will chip in: I always, whenever possible, try to reproduce the bug in tests first, before launching debugger /

Don't see the top comments mentioning that, so I will chip in: I always, whenever possible, try to reproduce the bug in tests first, before launching debugger / adding some statements, etc. Being able to quickly reproduce the bug time and time again makes a big difference. Some permanent verification that it's actually fixed (at least in the given case) at the end of the session is also nice and adds a lot when doing a major refactoring or something similar. Especially for bugs related to the domain specific requirements, rather than the technical ones.