Some say the secret is all in the preparation. Make sure you have the right materials and the right colours through tests using computer software and reading guidelines. The more time you spend preparing the better your personally finished door will look. It's probably best to hang the door first, then take it off and remove all the hinges and fittings etc. More often than not doors are supplied with a base coat of stain, so don't worry too much about this. If the door has no base coat it is probably best to apply a base coat prior to hanging. Always make sure that prior to adding a base coat make sure the door has had a good sanding. If there are any sharp corners you should round them slightly. If you are installing a new external door never fit the door then leave it for a few days before applying the finish.
When your are applying your finish coats it is important to apply your finish to all faces of the door in particular the bottom. You should include the hinge and other moving parts.