The instructions that come with tools are typically beyond worthless. They either leave out important things, mention completely irrelevant stuff, or make a big deal out of minor issues.
Some general tips:
Safety glasses when working with power tools. You don't need them when using a screwdriver, despite what the sticker on the screwdriver says.
Keep the guard in place on all grinders. When a wheel decides it's sick of being round, the results are not pretty.
If you can see the edge of a blade, wheel, etc, when using a saw, angle grinder, etc, you're doing something WRONG, and need to move your head or stop the tool NOW. You should never see a blade on-edge. If you can, it means you have insufficient guards in place, or are positioning the tool or your head incorrectly. If the spinning part were to break, your face would be its destination.
If you have a grinder, welder, or other hot particle generating tool, or even if you don't, keep a fire extinguisher handy.
If your circular saw has a blade guard, only lock it open if you're really cutting something it won't get through without snagging.
Make sure any tool where the power switch can lock on is not on when plugged in - drills with a trigger lock, drill press or any other tool with a non-momentary switch, angle grinder, etc.
Any handheld tool should be unplugged while changing attachments - it's too easy to bump the trigger manipulating it.
Yes, you can remove trigger safeties on many tools, even though the book will tell you in huge red letters not to. They're often so bloody annoying they do more harm than good. Just be sure to follow the rule above about unplugging it any time you don't plan on cutting something, and use common sense when carrying it, etc.
Wear gloves except when working with high-powered rotating machinery. the kind that'll snag your glove, then proceed to wrap your hand, arm, and torso around the spindle.
Nail guns, etc, are dangerous. Your bones are very soft compared to what they're used to putting nails through. Respect accordingly.
Umm, that's all I can think of right now, and I'm tired. Use common sense.
--Bushytails