Vintage Wristwatch Care - When choosing a vintage wristwatch, remember that early models often had to be wound by hand daily, were not shock resistant, and were not water resistant. For daily wear, a later model selfwinding watch featuring shock resistance and water resistance may be a better choice. These features began showing up in the late 40's and early 50's.
Your watch should be cleaned and lubricated every two years by a qualified watchmaker. Dirt increases wear and watch oils dry up with time and slow and eventually stop movements.
Keep your watch away from water. Moisture and rust kills more watches than anything else. Once rust attacks a movement, little can be done to reverse the damage.
It is a good practice to wind your watch every morning, and if you need to ship your watch, wind it fully before hand to reduce the chance of damage.
Modern Wristwatch Care - The same principals apply to care for modern watches as for vintage watches. Keep them wound regularly by hand, or with the use of a winder for automatic watches.
Although most modern wristwatches are shock resistant and water resistant, avoid excessive shock and exposure to water. There are special diver watches made for underwater use, but most wrists are not "waterproof".
Battery operated watches require care too. Change or remove the battery as soon as it runs down. An old battery left in a watch my leak and ruin the movement.
Avoid extreme tempatures, magnets, and harsh chemicals. Remove your watch when working on your car or other equipment to avoid scratching the case, bracelet and crystal.
In short, use common sense and your watch will last longer.