1. Wear Appropriate Clothing
Whenever working in the wood shop, remember to avoid loose-fitting clothing, as you wouldn't want any of your attire to become entangled in a saw blade or cutting head. Wear clothes that are comfortable for the environment in which you're working, but also will protect your body from any wayward wood chips that might result from cutting. Before beginning, remember to remove any dangling jewelry such as neck chains or bracelets.
2. Always Wear Safety Equipment
The first and most important rule of woodworking is to wear appropriate safety equipment. While hearing protection is necessary for some very noisy tools such as routers and surface planers, and latex gloves may be necessary when applying finishes, there is no time in the wood shop that you should be without your safety glasses. Put them on when you enter the shop, and don't take them off until you leave. Your eyesight is too important to take chances.
3. Disconnect Power Before Blade Changes
Whenever you need to change a blade or bit on a power tool, always disconnect the electricity to the power tool before even beginning the blade change. (Don't just check to see that the switch is off, as a switch could get bumped or malfunction.) Many a woodworker has lost fingers (or worse) by forgetting this simple but very important rule. I've seen woodworkers even go as far as to affix the wrenches to the power cables so there is NO chance they'll forget to disconnect the power.
4. Avoid Drugs and Alcohol
Intoxicating substances and woodworking are a dangerous mix. Stay out of the wood shop if you are even remotely under the influence of any intoxicants.
While it may seem harmless for the weekend woodworker to crack open a beer (or six) while working on a project, avoid the temptation until you're finished with the woodworking. You're going to be much less likely to encounter a problem if you're clean and sober when working with your power tools.
5. Use Sharp Blades & Bits
This one seems like a no-brainer, but a dull cutting tool is a dangerous tool. If a saw blade is not as sharp as it ideally should be, the tool and the woodworker will have to work harder to complete the desired task. In such cases, the tool will be more likely to kick-back or bind. Besides, a sharper cutting tool will produce a cleaner cut, so there are more than just safety advantages here. Keep the blade sharp and clean of pitch, and you'll be safer and have better results.
6. Try Using One Extension Cord
Here's a tip I've used regularly in the past. For all 110-volt power tools in the shop, I use one heavy-duty extension cord. Not one per tool, but one TOTAL. This way, I'm forced to switch the cord from tool to tool before the tool can be used. In this manner, you are always remembering to plug and unplug the power when moving from one tool to another, and you'll be more cognizant of the need to disconnect the power when making bit or blade changes.
7. Always Work Against the Cutter
Woodworking Power Tools are designed so that the direction that the wood moves through the tool (or the direction that the tool moves across the wood) is in the opposite direction of the movement of the cutting head. In other words, a router bit or saw blade should cut against the motion and not with it. The cutter should cut into the stock, not with the stock.
8. Always Check for Nails, Screws and Other Metal
Another no-brainer tip which doesn't bear mentioning, so that's why I'm going to mention it: Always check the stock you're preparing to cut for any metal (nails, screws, staples, etc.) before beginning a cut. Nails and rapidly spinning saw blades are not a good mix. Not only can this damage the cutting head and the stock, but at the very minimum, can cause the stock to kick back, which is a common cause of injury. Inspect the stock (or better yet, use a metal detector) before cutting.
