What's truly important is storyline and gameplay. Mapping, while important, should be one of the least of your worries for the most part. I would suggest drawing out a sketch of what you want a town/castle/dungeon to look like, in and out, and then go into the map editor, take whatever chipset you are using, and then try your damnedest to recreate that picture in your maps. If you aren't very creative, then I would suggest just making houses that fit together in an ideal way, and then surround it by trees, mountains, tall grass, dirt paths (all of which should be "rounded"), barrels and cut logs on the side of houses, and tree stumps to signify where the spare wood came from. Whatever you do, do not make every house in your village look exactly the same. For example, copy/paste of a single house to represent every house in one of your villages is a BIG no-no. Even if they are square, use different wall tiles and ceiling tiles, different windows and doors, and whatever else you can come up with to make each house stand out, if even by a little. One last bit of information... Use the different wall tiles for the outside of your house, I cannot stress this enough. I've seen a few games in my day that use just one of the brighter tiles (I've been guilty of this in my early years) for the entire outside of their house.
I'll supply a quick example, one because I'm bored and need something to do, and two that I find it's essential to provide a graphic representation of one's information.
What not to do.
A more acceptable, but by no means perfect in any way, alternative.
Before I forget, "practice makes perfect" doesn't really apply here. You could be using Rm2k3 for years, or a few days, and still come up with the same maps. Also, it's not a bad idea to spend some time on your maps. If it took you anywhere between less than a minute to 3 minutes to make your outer town map, I would suggest deleting it and doing it over. A good map should take you at least 10+ minutes, though 20+ is ideal. I'm sure that if you have the time to devote yourself to making a halfway decent game, you have enough time to work on a single map for as long as it takes to make it look good and function easily.
EDIT: Just noticed a couple of mapping errors in the second map example. I either needed to increase the height of the highest right cliff by at least one or remove the boundary that would separate the two cliffs at the top. The other being that one of the right corner cliffs along the top of the map is one tile too tall.