Since the worlds I create are based on ideas I have of prior to construction, I have a vision of roughly how the world should look. I draw the visible continent(s) manually with a mouse, then apply filters and brushes to mess up the coasts, and create lakes and additional islands. Another way is drawing an outline of the world, then generating random shapes with the cloud method in Photoshop and stitching them together to roughly follow the coastlines, removing and adding where necessary. With those methods, the world has a varied, detailed, less round appearance but fits the initial vision closely.