Aligning two stiff metal ends together so that they can be soldered is the hardest part of making a ring band. Excessive filing and sawing are what has gotten me into trouble with the sizing, and I fear that only practice will solve the dilemma. So for anyone else with this problem...here are a few tutorials for your viewing pleasure. Move over and share your popcorn, because I'm sitting next to you taking in all this information! Let's RING in the New Year!
First is a Wikipedia article on ring sizing, with a chart. Love charts!
Second is a great video on soldering rings with information on getting a good join before soldering.