On your first date, you probably weren't thinking about a marriage proposal yet, but I bet there was a spark and excitement.
Relive the magic of meeting each other for the first time by taking your sweetheart to the exact place where you had your first date. You can also recreate other details bring the same flowers you bought then, order the same meal, wear a similar outfit, or play the same song that was playing on the car stereo. Your sweetie will be touched that you remembered all the little details, and know that something special is about to happen.
When it comes time for the marriage proposal, reminisce a little, and then say something like "We've had an amazing journey together so far, and now I think we're ready to take the next step in that journey. I'm hoping you'll do me the honor of marrying me."
Pros of this Marriage Proposal Idea: You'll have an easy way to celebrate future milestone anniversaries relive the magic all over again! You'll win points for being romantic enough to remember the small details.
Cons of this marriage proposal idea: If you didn't have a particularly good first date, there might not be too much magic to relive. If you have a poor memory, you run the risk of recreating something incorrectly.

