I have a "bender" that is clamped in a vice and it works very well
http://www2.towerhobbies.com/cgi-bin...?&I=LXL786&P=7
For lighter stuff I prefer round nose pliers. Your 3/16" is pretty heavy duty. Usually, having a mandrel, like the shank of a screwdriver clamped in a vice, to bend the wire around helps prevent the fractures you are experiencing. It is possible you will need to heat soften and re-anneal the wire, depending on the severity of the bends you are attempting.