Telepost footing

I am adding a new telepost to take a bit of the sag out of a slightly sagging beam. Was planning on going with a 24" x 24" x 10" footing with rebar, but have read some contradicting info on the internet, so am posting here for clarification.

It is (and always will be) an unfinished basement. Does the post footing need a vapor barrier? Does the footing need to be below, even with, or higher than the finished floor? And what is the best way to connect post to the footing? Can I put the bottom of the post right into the wet cement, can I set some bolts pointing up into the wet cement or do I need to drill out the finished cement and use lag shields?

All opinions are appreciated and thanks!