I have this friend who always threatens to give me one of those Tiffany's blue boxes. If his knees weren't too sore from playing tennis, he'd probably even get down on a bended one. If I were ever going to let him, I would have to put him through my pre-engagement education program (patent pending).
Step one: show the scene from Bed of Roses when Christian Slater proposed to Mary Stuart Masterson in front of his whole extended family and she runs out of the room and demands that they go home to NY.
Lesson one: proposals are best in a private setting. There is no need to make her feel pressured to say yes or for you to be embarrassed if she says no. (Although it does work sometimes--see While You Were Sleeping for rebuttal.)
Which brings me to lesson two--don't ask the question if you don't know the answer. While the moment of the proposal may be a surprise, the fact that you're asking shouldn't be. In season two of the Gilmore Girls, when Lorelei tells Luke that Max proposed, he asks all kinds of questions--where will they live?, are they going to have kids, or a joint checking account? She is ashamed to realize they haven't discussed any of those things. And it is a discussion about Max's role in raising Rory (Lorelei's daughter), which helps lead Lorelei to call off the engagement.
And then, for me, there is a third lesson. While I would like an effort made, I don't necessarily need that special blue box, or 1000 yellow daisies. I think the key is that those unique touches be personally meaningful. For me, I'm a traditionalist and the things that I do need include a bended knee and I would like my parents to have given their permission first. Like I said, I'm a traditionalist.
Oh, and if you haven't learned anything from the cliche about hiding the ring in the food and the bride-to-be needing the Heimlich maneuver, then you don't meet the IQ requirement for marriage or reproduction.