Here's a quick tutorial to get back into the swing of things for 2013. I was asked about drawing coastlines. This is just a technique question so it's software agnostic.
1. Starting point
Here's the basic shape of the coastline - this is what I see a lot in turnover sketches at the early design stage. It's very blobby and indistinct, and looks nothing like a real coastline. The key is the regularity and smoothness of the line
2. Break it up!
I've followed the general shape of the coastline, but broken the line into a more jagged pattern. Some regions are almost sawtoothed. Try not to make features and variations the same size. Coastlines are fractal - they should look similarly broken up at a range of different zoom levels. Add some smooth coves for beaches to give variety (like the beach under the 2.)
Add islands along the coast. I tend to add them off peninsulas - where a spur of rock stretches out into the sea and leaves a trail of islands pointing out - or in inlets where the islands can mimic the shape of the negative space.
3. Edge detail
At this stage I've added a range of marks to the land to indicate the structure of the coastline and hint at hills, valleys, and the form of that beach I mentioned earlier. A lot of coastline has a sharp drop to the sea, and these lines hint at that structure.
For more hints and tips see the Tutorials section of my blog: [link]
Ask any questions in the comments and I'll do my best to answer them!