I would like to sleep with my hair in a bun for some nice soft waves in the morning when I wake up. Do any of you do this, and do you put any product in your hair, or wet it down? I would much appriciate any input! ;D

If you put your hair in a bun when the hair is damp, you will have lovely waves when the hair dries.  Don't let the hair get too wet/damp, or it won't dry by morning.

How do you secure the bun, with pins or an elastic?

I have used hairscroos for securing a bun while sleeping.  But you could use anything that will hold and is comfortable while sleeping.  My sleep buns are on the top of my head, so I could use pins, elastics, or scrunchies to hold it in place.

When I make a bun at night, it's at the nape of my neck. Once the hair is wrapped around so there is only a little bit left out, I tuck the end under the bun and it stays better that way. Then I wrap a big scrunchy around it and it stays. I would recomend a bun on top of your head if you like to sleep on your back, though. :D
Meg