Have the right tools for the job

These are the tools I think every tinkerer should have in their setup.  You can get more expensive versions of each of these tools, but these are the ones I recommend.

Solding Kit

Everyone needs a good soldering kit, I have a $120 hakko soldering station, but I end up using my cheap portable iron 90% of the time.

Wire Cutters

The difference between nice wire cutters and cheap ones is night and day.  Spend $5 and get a pair that will last.

Multimeter

A multimeter allows you to easily troubleshoot your projects when something isn't working.