Bias binding is one of those things that are intimidating until you do it a few times. At least it was for me. Here is a link to a site that shows how to do this step by step with good pics. It's the same way I do it and it works very well.
http://modernquiltlove.wordpress.com...-bias-binding/
You need to start out by measuring the linear inches (2 * (width + length)) of your quilt. Then, determine the size of square you need to start with for bias binding.
I have a really good little book that I highly recommend every quilter have. It's the All-In-One Quilter's Pocket Reference. It's a little spiral bound book that has lots of information for quilter's. Included is a chart that has the size of square you need to get the linear inches for bias binding.