Bridal: Put a ring on it

Whether he goes it alone, she compiles a secret stash of photos or they brave diamond shopping together, choosing an engagement ring is perhaps the most significant purchase a couple will make -- and the first step toward their wedding day. But while a diamond ring is still a symbol of tradition, it's no longer just a traditional center stone with two baguettes. What's on fire? The pros share the scoop on the rock stars of 2012.