Well hello Obliro, welcome to the Guild! You have come to the right place. The people here are both knowledgeable and friendly, so feel free to ask questions with impunity. Do you have any map-making software of your own yet, or have your previous maps been hand drawn? Most of the members of the Guild make their maps using some form of software or another, but there are a few that draw them by hand. You can find a great beginners introduction to map-making here (this is really the place to start):
You can also find all sorts of great map-making walk throughs in the tutorials sub-forum. In fact, regarding your worries about rivers, here are a couple of good threads on getting rivers in the right spot:
Of course the best and fastest way learn (or to improve) fantasy map-making is simply to do it. So I encourage you to check out Ravells "Quickstart guide," peruse the tutorials section to find a style that you like, acquire the software needed to make the map, and get to work! Also, when you do this, feel free to post your fledgling work-in-progress map in the appropriate forum and you'll get all sorts of helpful feedback from the Guild. Happy map-making.