Here are some other great tutorials I found on Pinterest.
Ruffle Curtains from The Shabby Creek Cottage
Curtain Topper by On Sutton Place
Gathered Curtains with Ties by Make It and Love It
Ruffled Curtains by Flamingo Toes
Gathered Top Curtains by Make It and Love It
Striped Curtains by High-Heeled Foot in the Door