As far as what to include on the map, that's up to you. It all depends on what you're looking for, and the purpose of your map. Most map-makers will tell you that real world geography is important to take into consideration. Unless your world is "fantastical" in nature, and defies logic. Keep in mind the natural flow of rivers, as this is very important. River placement can be a hard lesson for first time mappers, so search the forum for tutorials.
Good luck, and have fun!