Look for a fabric with a diagonal weave, as this is the most supportive weave for the baby. The weight of the fabric is up to you. it should be at least 4 1/2 yards long, and it can be 6 yards long if you need that much. I have a fleece wrap that I made, and it's a little over five yards, plenty for me to do the more involved carries. The fabric shouldn't be any narrower than 20 inches, and anything wider than 30 inches will give you too much bulk. For back carries, I would recommend it be at least 22 inches wide. You'll need to hem the edges, and you may want to taper each end so you'll have a smaller knot. Have fun!