Wear a properly fitting helmet. Your helmet should not be uncomfortably tight, but it should be tight enough that it doesn't wobble on your head. Also, when selecting a full face helmet, ensure that you are able to see well, including in your peripheral line of vision.
Check your tire pressure regularly. Not only will improperly inflated tires wear poorly, they can also become damaged, compromising the integrity of the casing, leading to catastrophic failure. Also, the wrong tire pressure can negatively affect your bike's handling.
High quality motorcycle gloves are a very important protection in the event of a crash. When we fall, we instinctively put our hands out infront of us to break the fall. Protect your hands from damage with quality gloves.
Check the age of your tires. Old tires dry out, reducing their strength and their traction, increasing your chances of crashing. Many experts recommend keeping your tires no more than 5 years since they were manufactured.
Assume that cars can't or won't see you, and ride defensively.
Slow down in the rain. Water acts as a lubricant on the road, reducing the amount of traction you have available. Allow more time to accelerate, brake, and corner more slowly.
Don't drink and ride. Riding a motorcycle requires extreme concentration, fast reaction times, and fine motor control, and these are all impaired by alcohol. Not only is riding while drunk illegal, it is extremely dangerous.
Always have an out. Ensure that you always have an out in traffic, which you can take to avoid an accident.
Avoid hitting pot holes. Pot holes are not only annoying, on a motorcycle they can damage your wheels, causing an accident.
Watch out for painted markings on the road, especially when it's wet. Painted surfaces generally have less traction than asphalt, so avoid cornering, braking, or accelerating on them in wet conditions.