I like to heavily starch the fabric before cutting the binding strips. This makes them more like straight-grain strips so they don't stretch out of shape easily.
Here are links to Leah Day's videos on sewing binding. Might help you with the corners:
http://www.youtube.com/watch?v=wprg5vzkuGw
http://www.youtube.com/watch?v=7MRfA...eature=related
I too love strips on the bias for binding. Always makes a great finish!