I used my table saw because that's what I have. On mine, I can change the angle of the blade, and cut it to the correct angle. It's just a miter cut, but instead of 45 on each side, it's 67.5. You can also use a hand saw and a miter box, a chop saw, miter saw, or radial arm saw.
Unfortunately, I don't think I have any close pics. This one I think has the finished product though.
Re: Corner Cabinet Trim
One thing that you will notice on this pic is that I have a non-standard installation of the trim. Instead of using cover panels, I mitered all the corners and took the light rail all the way around the corners.
Kristen