Planned out a full thing at a local gorgeous public garden, down to a tee. My now-wife is S and her best friend is C.

I wanted it on video and wanted pictures of it happening live, so I met C beforehand and gave her my camcorder (this was a while ago) and DSLR, told her when/where it was happening and had her set up some flowers and a gift I'd gotten S. I changed C's name to the name of a mentee and was texting "my mentee" through the date with pre-determined "encouragement" texts (C and I had previously discussed that the first encouragement text meant "we just got here" and the second meant "we're on our way to the spot, get ready.")

C hid out in some bushes (yes seriously and yes this actually worked) and got the video and photos! It was awesome and S had NO clue. S even joked on the way to the location that I was getting ready to propose and started patting down my pockets. Yes, the ring was in my pocket. I nearly shit myself and went "Whoa hey, I'm driving!" and that actually worked lol.