We went with a really gorgeous aquamarine instead of a diamond, and I had her best friend help me decide what we both thought she would like. That said, there's nothing wrong with taking her to pick out the ring, herself, and still surprisingly her with the where and how. She's going to be the one who will be wearing it, after all. This doesn't sound like it applies to your situation, but it needs to be said for others where it might; while the actual act of the proposal can be a surprise, the idea of proposing to her *never* should be. You should be every bit as already assured of what her answer will be as you are of you wanting to ask, well before you even think about buying a ring, etc.