My best advice for anyone is to do this: close your eyes, relax, breath, and think. Think about what sort of places the people are going to go to...desert dunes, frigid polar regions, jungles with gorillas, etc. Once you have it in your mind these sorts of things, think about how long it will take to travel to each place. Now you know what the continent should have...what sort of areas need to be there and how far apart they should be. Open your eyes and sketch something, anything, on paper. It doesn't have to look great but should look more than just a giant circle that says "world". Look at some other maps to see what coastlines look like...all jagged and in and out with weird shapes. Try to sketch something really jagged like broken glass pieces. Then go back and add detail. Then add more detail...refine refine refine until you get something that you like.
Now that you have a shape go back and put in things like rivers, mountains, forests, and canyons. If you find that things are too close together and don't fit the story quite right, just refine the coast somewhere to make it fit. When all else fails, ask one of us to draw ya something