Hi there Limanerg, welcome to the Guild.
First off, do you intend to create your own map, and are simply asking for advice on how to go about doing so, or are you attempting to commission a map? If the former, then I recommend browsing the tutorials section where you will find tutorials aplenty that will help you on your way. If the latter, then I recommend you post an add in the Map Requests forum, but make sure that you read Ravells sticky on how to post adds before doing so. Either way, good luck on your project.