Here is what the old seat covers looked like--not quite my style.
Here are the supplies you will need: fabric, staple gun, yard stick, and a good pair of scissors.
Cut the fabric to a desired side. Thankfully when the fabric is stapled underneath, you can't tell how straight you cut the line.
You will only want about 3 inches extra on either side. If you have too much extra underneath, it makes the corners difficult to execute neatly.
Pull the fabric tight and staple all the sides. Next--the corners.
Flatten out the corners and staple.
And here is the final product! Much nicer! It was super easy and only cost $15 to cover 6 chairs! John and I might go into the reupholstering business!