This excellent tool, courtesy of Cmdr Drygin who is working with the Canonn R&D team, allows you to easily find a set of coordinates on a planetary body from any starting point. Basic usage is as follows:

1. Approach planet until you reach Orbital Cruise.
2. Stop ship completely (normal space).
3. Enter current and destination coordinates.
4. Align ship compass with given bearing.
5. Jump back into Supercruise and proceed to destination.

ED:Bearing – http://www.hotdoy.ca/ed/bearing/

Also provides many notable locations’ coordinates pre-filled to make life even simpler.