When putting a quilt on the frame before using the longarm, what do you mean by floating the batting and the top?

It means that you only baste the batting and top to the backing fabric at the top. Then quilt.

You load/attach the backing (being sure it is squared up) to the leaders (top and bottom), then attach the batting and top to the backing and let the lower end "float" without attaching the lower(bottom) end to the rollers. Works well for me :-) It allows me to "fluff" the top and batting once in a while and make sure it's lying nicely before doing the next pass....

Do you just float the top or do you float the batting also?

I float both. I only load the back.

I float both ... from the very beginning.

Same here until I get to the very bottom, the I pin the bottom or stitch it down so it stays straight while quilting it.

This is a very personal thing with LA quilters. I pin my backing, batting and top to my take-up leader, pin my backing to its leader, float my batting and pin my top to its leader. I prefer a more stable, tighter surface when I quilt, but that is just my personal preference. You can see in my avatar that my top is attached to it's leader and the batting is floating.

Ditto for me. It's easier to keep it square and deal with any un-squareness, lumps, wonkyness this way.

I'm a control freak!! I attach the bottom of the quilt top to the roller.