Using a dremel cut off disk, when making deep cuts in a cylindrical object, go around and round, don't go from one side straight in.
Also when cutting metal with a cut off disk, keep a powerful magnet near the piece to minimize sparks.
Make sure the thing is fucking off before you plug it in.
If you left your soldering iron on a table without a stand, make a mental note to NOT catch it by instinct if it starts falling.
Watch out and patch melted wire insulation right away.
Drill presses should not be placed near a peg board (or similar tool holding device).