If you use super glue, be careful. I believe that the previous owner of my lp super glued a new nut in and spilled thus ruining the headstock finish. I'm not complaining though, I got it cheap and it sounds great.
A drop or two of superglue used here - seems to work nicely. Surprising how many new guitars have a loose nut when you take the strings off for the first time. Easy fix though.
I use 1/2 Elmer's and 1/2 water. Just enough to hold it. Easy to pop it out and clean up too. I figure that 99% of the time the nut is held down tight with string pressure. It's not really going to go anywhere. Just enough adhesive to keep it there.