The mechanics of it:
Some people take the quilt from the washer and dry it for 10 minutes or so on warm then remove it from the dryer while it is still damp and proceed to block it.
I usually dry it all the way, then take it and block it, using a spray bottle and plain water to re-wet it. (Not sure why - just habit.)
You lay the wet quilt out on a carpeted floor. If it is dry, wet it with the spray bottle after it is laid out -- enough so that it is not dripping, but is pretty darn wet. Then, starting in the center of each side, begin pinning the quilt to the carpet, using nice strong straight pins (NOT those thin silk pins) and STRETCHING the quilt a bit as you go. (It helps to work with 2 people on this, each on opposite sides of the quilt.) Work your way around the quilt so that it is pinned to the carpet every 2" or so. If "puffy" areas develop in the center, pat them down as flat as possible, distributing the bulk evenly. You will be amazed -- these will dry flat!
As you do this, you want to be sure your borders stay square, so I lay my large square ruler on each corner and border to make sure that those are stretched to 90 degree angles. Even some pretty stubborn border issues can be fixed this way.
When you are done, spray it one more time with the spray bottle and LET IT DRY COMPLETELY!!! NOTE: This may take a while -- even an entire day, depending on the weather -- but that's okay.
When it is dry, that quilt will be square as anything!
Try it -- you'll like it!
Beth, MI