I have wooden doors in my house which are very old. I want to repaint them. How can I do this by myself?

Firstly you will need to undo the hinges on the doors and place them in a ventialted area where you want to paint them.

Then sand the doors and remove any old paint, this also helps rough up the surface for the new paint to stick to.

You can buy a paint primer to help the paint stick. (I have never used it but you are supposed to)

Then it's as simple as taking a brush/roller and painting them.

Once they are dry, re-screw them to the hinges and you will have nice fresh doors :)