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Consider making the continent shaped like a dragon or something. Then nobody will complain about the realism.

If you want the realistic approach in a hurry, draw 3-5 random curves for mountain ranges. Imagine the range is taller in some part, and lower on another, and remember that a mountain range can become a string of islands if it gets low enough. Fill in some larger between-mountain pockets with flatter land (smooth coast) and some of the outsides with smaller flat areas and scrungly coasts. Draw some rivers - they go downhill and merge as they go until they reach the coast, and there's a lot of merged rivers in those between-mountain pockets. Pick a prevailing wind direction. From the edge of the map, imagine the wind picking up water as it goes over the ocean, dropping it off as it goes across the land, and dropping lots off as it goes over mountains. The wettest areas are forests, the medium areas are grass lands, the dry areas are desert. If your continent is really big, you can pick another random direction to bring water in from, so it's not all desert. Remember that deserts are mostly not the sand kind, and could look like the Eurasian steppe or the American Badlands.

Mountains are usually political borders. If there's a river near a border, it'll be the border. But larger rivers are just as likely to be the center of a polity as they are to be a border.