Admittedly with the longarm I haven't had to baste anything in a while, but back in the day this was my favorite method of basting. It's one no one really mentions and I'm not sure why, because the results are excellent, especially for larger quilts.
It's not something revolutionary, though your back may think it is. It's table basting.
That's right, no more crawling around on the floor!
Of course the essential part to this is tables. Most quilt shops have classroom areas with large tables all of the same height and when there aren't classes in progress, most will loan out the space for basting! No quilt shop nearby? Try a community center or church or other organization that you're associated with. But a quilt shop really is the best, and not just because you can do a little shopping.
Move the tables together until you have a surface large enough to accomadate your quilt back, then baste just like you would on the floor, minus the sore back and knees! Of course there are a few things you should keep in mind. If you're planning on taping your backing, ask first to make sure that's ok. And use good quality painter's tape that you know will come off easily. Some places won't allow tape, if that's the case extra large bulldog clips will often work or you may have to invest in some clamps from the hardware store. Or just find another place that lets you use tape! Also I've only ever used pins when table basting. If you want to spray baste I'd also ask about that before starting. The shop owner may be concerned about residue on the tables or have staff whose lungs, like mine, can't handle stuff in spray cans.
One of the best reasons to table baste at a quilt shop has to do with batting. Working on a large quilt at home it's almost impossible to get the batting perfectly smooth. Well, at a quilt shop everyone is going to be coming by to see what you're working on. So there'll always be an extra set of hands to help you give the batting those few extra tugs that get rid of all the creases and fullness. I've found this really is the secret to basting that works and doesn't need constant re-adjustment when you sew. And hey, talking to other quilters is just fun - even if they love brown and batiks, you can still learn from each other!