Question about making a map

Since I am not good at using any paint program can I draw it. So I get some blank piece of paper and draw a map. Then color it and all that stuff. Any writing about the map I may need for others. Then scan it in to my paint program. Then I can make the proper sizes. Will that work? Then my problem is doing the coordinates for the map. I seen the stuff they have here about it, but not sure how they come about making the coordinates. How do you know the numbers? Thanks for the help.