I know what you're talking about! I took me quite some time to figure out a good place to baste as I can't get on the floor either. This is what I do:
I generally do stabalizing stitching all around the perimieter of the quilt first. I do it in the ditch. Then I do the same along the sashing. Vertically then horizontally All in the ditch. That should give you more than enough stabilization for a wallhanging sized quilt. Then start to quilt whereever you like but I generally start in the middle and work out.
Good luck and don't forget to breath! You'll be so proud when you're all done. I hope that you'll post a pic! :)