David, congratulations. I remember going through the experience myself and it is an incredibly exciting time.
Take time finding the right moment, you've waited to get until this point and a few more weeks or months will be well worth it if you are able to create a situation that is memorable for the two of you.
Jason
PS: It goes without saying that the primary advantage to a carefully planned proposal is that it is much harder for her to say no.
[and it will also earn you lots of points with every other woman she knows for at least the first year of marriage, after which there's nothing you can do to keep your name from being MUD anyway]
Seriously, congrats!