"One, the guy shouldn't be asking her to marry him if he doesn't know her style, or doesn't bother to ask around with her friends and such what her style might be. Second, I tell each guy, if she doesn't want to marry you because of a ring, then don't marry her."
i have to say that i am in complete agreement with this also. how wise.
when DF proposed, i HAD NO IDEA... i knew the time was coming because we were definitely at that point in our relationship, and i could tell he was saving money. but in the end, he blew me away... when he got down on the knee and i saw the ring, i was in complete shock - it was EXACTLY what i wanted: emerald cut, simple solitaire platinum band setting. i was amazed how he got it right - we'd never discussed or mentioned diamond rings before (although he is very perceptive and knows my jewelry style), but it turns out when the time came, he found one of my best friends on facebook and emailed her asking for her help - what a smart man! of course, she knew exactly what i wanted as we had talked about it many times before.
i am so touched thinking about DF going to jewelry and diamond stores, researching everything himself, and in the end, picking out the perfect stone for me. there is something so special about that, which i think you lose if you pick out the ring together.
believe me, i am a VERY PICKY person, and i don't know what i would have done if he picked out something i hated... but the fact that he did it by himself, AND GOT IT RIGHT definitely says something to me.
(the only thing he got wrong was the ring size

... he had no idea as i don't own a ring for my ring finger, and they advised him to go with the popular 6... turns out i am a 3.5! so i had the setting changed to my smaller ring size, but otherwise, everything is the same)
i know different people like to do it differently, but i'm just saying how for me, i would never have wanted to go ring shopping together...