I prepare the area by clearing a large space on the rug in the bedroom and spreading out an old flannel sheet. The carpeting works because I can pin down into the carpet pad, and I use the bedroom because I can close the door and prevent the cats from strolling around on the quilt while it's being blocked.
The sheet helps to protect the rug from getting wet, although the quilt never gets wet enough to soak through to the flannel anyway. (Plus this way I can save my favorite old sheet with the little sheep on it.)
I also assemble various straight edge tools and my biggest square cutting ruler for squaring the corners, a tape measure, a box of T-pins (I've used the larger glass-head pins too... but fine ones with thin shafts aren't strong enough), and a spray bottle full of water set to mist.
Here's how bad and warped this thing looked before blocking. Usually my quilts aren't THIS distorted, but the linear pattern I used seem to really distort things badly. Never fear. It'll fix right up.
Basically, I spray the whole quilt liberally and then start smushing it around (that's the technical term), pinning, straightening, pulling, spraying more, smushing more, pinning more, spreading, unpinnining, spreading, smushing, and pinning. You crawl around on the damp quilt a lot so you end up with damp knees. You get the idea. Smush, pin, measure, unpin, smush, pin... until it's the way you want it. It usually takes me pinning one side, straightening up from there, then working across the quilt to smush things in line several times before it's the way I want it.
Here's a not-quite done look:
Much better, huh? When I have it the way I want it, I give it all one last spray, then I walk away and close the door and let it dry ALL THE WAY.
You do have to be careful about this if you've not preshrunk your fabrics and think something might bleed, by the way. Also, I'm told that this doesn't work as well if the batting is 100% poly, as that won't give the way cotton does. I always use cotton batting (actually, the 80/20 Hobbs Heirloom) so I've never had any problem.
Now, you can sit and have another cup of coffee and gaze proudly at your quilt. That's what I'm going to do.