Honestly, if you want to make a good map, just start. The number one hardest thing to do is start. And it is still difficult for me. But you just have to get over that first boundary of looking at a blank page. Just do something. Put down some houses, some cliffs, some rivers, lakes, paths, maybe a few trees. Then look at it, imagine what it could be, and store that in your mind.
Use your own perception to get some feedback about what is missing. Do you look at your map and say "This sucks, it's a box map, it's full of empty space and nothing to look at, but I don't know how to map, and I am afraid to do it, and lazy so I am just going to leave it like this and hope nobody notices", or do you say "What can I add to this? What can I subtract from this? What needs to be changed? What can I do with my current tileset do make it look more natural, more detailed and complete? Are there any parts that stick out as being too straight or too bare?"
This is where referring to maps that you like comes in handy. By looking at these you can start to pick up the patterns in good maps, but they mostly boil down to staying away from long straight lines/right angles (as much as possible) and not having swaths of empty, unchanging space.
The secret is to iterate. Use your intuition, as well as your own eyeballs. Start with the basics and then add details. Don't be afraid to experiment either, it is 80% of figuring something out. The great thing about RM is that you can always update bad habits. Even if you want to skip this map for now, you can always come back to it later. But please don't present it to other people until you are proud of it, otherwise you will be wasting your first impression.