Lots of good ideas, thanks everyone!

I have 2 design walls, and they're usually both occupied. So....I use my king-sized bed to lay out my blocks; then I put a piece of paper on the first block on the top row left, with A-1 on it. Then I pick up the blocks, always keeping the A1 block on top. First row done. Then I move on to the next rows, labeling them B1, C1, etc., stacking, and removing them as well. Using this method, the blocks are easily removed and sewn into the quilt in the order you intended. Oh, and I also take a picture as I go just to be sure!

Wow! I love this idea! I usually use post-its and pins to keep my stacks together. Also, I lay my block pieces ready for stitching on cardboard squares from the packs of scrapbooking paper. These are 12 x 12.

I label them, too. I have a fairly small place, so sometimes I lay out only two or three rows at a time. I can keep like fabrics from butting up against each other that way. I pin a piece of paper to the left edge piece of the row labeled with the row number and an arrow indicating which way is "up" (towards the top of the quilt). You can get them looking pretty good this way without too much layout room.

When I make the scrappy quilts, and want some order to it, I lay out the pieces and just over lap them. That way I can make sure I am not putting 3 blues together, and it is pleasing to the eye. And I do about 6 rows - sometimes 7. And then as I pick them up, I always go left to right and then pin them together with the first one is going to be the far left piece. I leave the note pinned to the left piece and then I know when I pick a row up which direction it goes.

I was forever sewing the rows together and then realized I had put them together upside down. This step helped me to keep them in order.

If you buy bread with the plastic tags on it, keep the tags. You can label the tags with a permanent market, A-1, B-1. etc to designate rows and pin through the little circle opening so they won't fall off and use them again and again.

Stack them up in colors or patterns for as many rows as you need and then sew top one from each stack. continue on...

When I have these rows of blocks laid out the way I want them (usually on my bed), I pin numbers on the first block in each row. Then I turn down the second block of row one and put a pin where I will begin to sew that seam. Flip that back up and turn down number three. Pin that and flip it up, etc. I can get the whole thing pinned and to the sewing machine, and I can sew it whenever. Everything is numbered and pinned. When all rows are sewn, sew the rows together.
Have fun!

Or,
you could do as Alex Anderson said, "shake them up in a sack and draw them out one by one, and no changing."

You've heard of the 800 lb. gorilla in the room? That's what my scraps are to me! Boxes and crates and bins of scraps. I take them out occasionally to pet and rearrange them and try REALLY hard to envision making a scrappy quilt. Then my OCD takes over and back they go into the closet, under the bed, etc. It's just pitiful. I think I may need an intervention!! I really admire all the beautiful scrappies everyone has posted, but can't seem to make myself "just do it". Thanks for this post and all the wonderful approaches and ideas. Now, back to my sewing room to admire my scraps. Please PRAY for me!!!