The average door can take a lot of abuse in its lifetime. After a while you start to notice a squeak here and there or one day it refuses to budge. Proper maintenance and care should be followed in order to keep your doors looking and feeling like new.
Wooden doors may need some extra maintenance. They are susceptible to the weather, when wood absorbs water it expands and contracts in the heat. This constant expansion and contraction could lead to warping and twisting. If your door is not protected by a porch or over hang it will require more frequent maintenance. The ultra violet rays of the sun can really do a number on your door. Regularly apply a good stain or paint to the door to help seal it and protect it from the elements.
Wiping down your door is a good practice to adopt, this helps remove any acidity that has accumulated from pollutants. Thoroughly inspect your door for cracks. You should apply a fresh coat of polyurethane every 12 to 18 months. Simply apply a light sanding on the outside of the door, get a clean cloth and apply a little paint thinner to it. Wipe down the door as thoroughly as possible and let dry. Make sure it is completely dry. Now apply a coat of polyurethane over the door. Be sure to cover the whole door properly fill in as many cracks and crevices as you can with the polyurethane. This should help preserve your door for another 12 to 18 months.
Hinges and locks should be lubricated at least once a year. When lubricating door hinges you have to first remove the pins, by gently tapping the pin upward with a nail and hammer. Spray the lubrication the pin and replace it. Move on to the next hinge.
If your locks are sticking here is a simple way to lubricate door knobs. Spray some lubricant in the key hole and on the key itself. Insert the key into the keyhole and turn it. Keep inserting and turning until the lock is free. If the lock doesn't come free you may have to disassemble it and clean it properly. You can find tutorials on how to disassemble a lock on the internet.
Remember that a careful and consistent maintenance schedule is required if you want your door to look and perform like the day you installed it. Inspect your doors regularly and make a schedule, this will make maintenance easier.