How should I plan a proposal?

I’ve been thinking a lot lately about proposing to my girlfriend. Part of me knows marriage changes a lot, because your plans and decisions aren’t just yours anymore, but at the same time I honestly can’t picture the next ten or twenty years without her. So I’m pretty sure I’m ready, I just don’t want to blurt it out over dinner one night and regret how little thought I put into it. I’d like to set up something romantic, give her a ring, and actually make the moment memorable. How would you organize the proposal, and what kind of ring is a safe bet when you want her to really love it?