While every mapmaker strives to make the most visually appealing map they can imagine, you have to remember that the purpose of a map is to convey data clearly to your audience. In my career, I have made maps for planners, engineers, rangers, hydrologists, lawyers, field crews, surveyors, elected officials, and the public, just to name a few. If I was working on one project that involved all of those groups, each map of that project would be different than the other. Finding out who the audience of a map is? should be one of your first objectives.
With this figured out, you have a clearer goal of what data you will need and how to show it. Don't be afraid to ask questions; a lot of times you can be pulled into a project in which you have no background. It is more appropriate to ask a lot of questions in the beginning, rather than in the middle or towards the end of a project.
I typically ask the following questions when I get pulled into a project:
Who is the audience of the map?
What are you trying to show?
Does any data already exist?
Will there be any analysis?
Will this be updated regularly to show progress/change?
With these questions answered, I can usually feel comfortable enough to start a project. This will help me form a guide on how to formulate a work plan to solve this mapping problem.