In order to create contrast within the four patch blocks, especially if I'm using just medium-colored fabrics in the block, I match homespuns with prints, plaids with florals, and so on.
When I'm happy with the way the design looks on the wall, I carefully transfer the squares to my sewing table. After all the time spent arranging them on the wall, I don't want to mix them up when sewing them together. By the way, I've discovered a new best friend in my digital camera. If a strong wind (or a husband) comes along and causes a few squares to fall off the design wall, I can refer back to previous pictures to remind me of how they'd been arranged.
This is when I save time with chain piecing--sewing the squares together in the order in which I'd laid them on my sewing table.
When I've sewed the squares into pairs, it's time to sew the pairs together into four-patch blocks. It's a slow process, but I love watching the "dream" come together in front of my eyes!