How do i get away from using straight lines?

[Midgardsormr]

Maybe you should start with city maps, where all those straight lines and perfectly square angles will be a blessing!

[Marion]

Try this tutorial: https://www.youtube.com/watch?v=BlYRWvpj1GE

It can greatly help with making the coastlines, adding lakes and so on. While it won't fix the part about rivers, it allows to turn almost literal square into an interesting map.

[jbgibson]

I know nothing about your workflow, but if the phrase MAKE an erratic line is acceptable instead of to draw one, you could try various ways of generating "randomness". A nice starter set of unpredictable lines can be had by taking photos of clouds, and doing different edge generation steps. Posterize it, run the number of posterization steps up and down, copy, distort, blend layers. One thing this can give you is varying fractal degrees, where some software-generated fractals are stuck with one fractal degree at a time. Think 'amount of roughness'. A sweep of barrier island beaches will be irregular, but in a different way than a jagged drowned-fjord way. Different clouds on different days will have immensely variable looks.

Heh- if you zoom in far enough to some rough line work, like the delightful roughness of the Fractal Terrains world generator, you find a bunch of (tiny) straight lines and smooth curves. Maybe just do your drawing all nice and comfortably straight/angular/geometric while zoomed in a zillion times, then zoom back out to see if it might look a little more natural.

Or make use of your carpentry: I know a guy who makes drop-dead gorgeous topographical maps starting with wood grain.