1) Cut your fabric to an appropriate width. Mine is eh-looks-about-right X good-enough inches. Hem the two long sides. I just fold in the sides about a half-inch and pin it before sewing a straight hem. Then fold in half the long way.
2) Press the fold firmly. You really need that middle fold line.
3) (This is where we all remember that I've only been sewing for a couple of months. It should have been folded with the right sides together. It doesn't really matter though.) Sew together the short sides. Don't worry about folding in the yucky ends, it won't matter when you're done.
4) Open up the middle fold and flatten the hemmed ends against the back of the fabric, creating a point. Press very firmly again.
Here is a photos of our new furniture and the pillows I made. There are more on my craft Flickr.