Step 1: Go to the fabric store (I like JoAnn and Hobby Lobby), and get 30 inches of fabric. I used to get one yard, but I discovered that it made the scarves extremely long.
Step 2: fold the fabric in half length-wise, and cut it along the fold
Step 3: Lay the fabrics front-to-front (the pretty sides of the fabric facing each other), then pin one end of the fabric together.
Step 4: Sew the ends together, then press along the stitches to get a nice seam
Step 5: Fold the fabric length-wise and front-to-front again. Pin the edges of the fold together
Step 6: Sew along the pins, about 1/4 of an inch away from the side of the fabric
Step 7: Turn the fabric inside out so that it looks how it would if you were going to put it on
Step 8: pin the two ends of the INSIDE fabric together, and sew it together
Step 9: Fold the edges of the opening under, then pin it so that it has a nice seam
Step 10: Sew the ends together, as close to the edge of the fabric as you can
And there you have it, your completed infinity scarf!