Install curtain rods that will not rust. The easiest way to put up curtains each year (if you live in a climate that has snow during the winter months) is to find rust-free rods you can leave up the entire year. Install the rods first, then measure after you have them up.
Measure the distance from the rod to floor (or where you would like the bottom of the drape to hang.) Multiply that number by two. Then, add three inches for hemming. This number will be the length of material you will need.
Now, measure the width across the curtain rod. Add three inches for hemming. This is the width of material you will need. Decorating fabric often comes 60 inches across. If the width you need is close to 60 inches, it's a good idea to use this width and just bunch up the fabric to make it fit on the rod.
Purchase outdoor quality fabric. This type of material is heavier and made to withstand the outdoor elements. Use extra strong thread and needle (made for sewing jeans) in order to hold up to the thicker, outdoor fabric.
When you have the fabric cut to the length you need, fold over the edges and iron down. Each edge should be folded over about an inch. Sew the edges in place, making one long hem the entire length of each side of the material.
Turn the fabric inside out. (With right sides facing together.) Pin in place, and sew from the top down one inch and a half. Do the same thing on the other side. Then, sew across the top edge. Secure your thread, and end off.
Measure three inches down from the ending point where you left off. Sew down one edge and up the other. You have just created the "hole" that you will put through the rod. Turn fabric inside out by pulling through the hole. When fabric is right side out, iron down the edge of the "hole." (You won't need to sew these as they will lay flat.)
Your curtain is complete! Put the rod through the hole and hang. If you'd like, create a sash by using extra material. Tie around curtain.