It's great to see that you have some interest in making some melee maps.
But to actually begin making serious melee maps, check this guide:
http://www.staredit.net/index.php?showtopic=10191. It's really helpful in starting with the basics.
The best way to learn is to look at the MotW maps from
http://www.broodwarmaps.net Click on the link at the right that says MotW and check out those maps. ALl of them are good and should provide fine examples of what great melee maps are like.