First I begin by pressing all of the fabrics, the backing and the finished quilt top. This is also a good time to snip any threads that are on the right side of the quilt top, or on the edges, that are long and may get caught in the darning foot of your machine.
Then I lay the backing on the floor (make sure you clean your floor first!). Lay the backing right side down and smooth it out as best you can. Always work the wrinkles out from the center to the edges, rather than from one end to the other. Next, use masking tape (not painters tape) to tape your quilt down.
I start on one edge in the middle, then go to the opposite side in the middle, then repeat so all of the middles of my edges are taped. It is important to pull the fabric taut before you tape it down. Next go to one corner and tape it down, go across the quilt diagonally, and tape the opposite corner down, pulling taut before you tape. Repeat this as well. Once I get the middles and corners done, I fill in the empty spaces with a little tape. The end result should look something like this.
Next I lay the batting down. I use 100% cotton batting. It naturally "sticks" to the cotton, so I roll the batting up into a log and line up one of the edges and roll it out onto the quilt back. Once it is laid out, I smooth out any wrinkles, again going from the center of the quilt to the edges.
Once you have made sure your batting is smoothed out as best as possible, lay out the quilt top on top of the batting the same way you rolled out the batting. Roll it into a log, line up one of the edges, and then unroll it. Then smooth from the center to the edges.
You can see from the picture I let my backing and batting overlap the edge of the quilt top by about 2-3 inches, that way if the top shifts a bit while quilting, I don't have to trim any of the quilt top before adding the binding.
I use Kwik Klip to help me close the safety pins. It is well worth the ten or so dollars it costs :) Also, because I am basting on floors that scratch, slide my cutting mat under the quilt so I don't have to worry about scratching up my floors, and I can also be sure I've made it through all of the layers of the quilt.
I place my pins about 4-6 inches apart, depending on the complexity of my quilt top. The more complex the piecing, the more chance you have of ending up with a pucker because of the seams, so pinning closer together helps the avoid this.
So there you have it, a basted quilt! It only took... two hours!! (Or at least that's how long it takes me :)