Great first effort!

What software are you using to draw it? If helps if you put the software you're using to draw your map in your profile information so that we can help you with advice specific to that software.

Couple of pointers if you are just starting out:
If you are using Gimp or photoshop, then you might want to try Old Guy's tutorial to get a crinkly coastline. (do a search on Old Guy and coastline and you should find it)
Almost all of the time you want to start with your landmasses in black and your sea in white (or vice versa) and keep that on the bottom-most layer as a reference. This makes it easy to use layer masks, clipping masks etc which in turn makes it easy to draw stuff on the land without it going into the sea and vice versa.

Welcome to the Guild.


Cheers

Ravs