Make them longer, hang rod higher if too long.

Are the window an average height?

If you buying or renting can you have someone email the measurements?

Heck why not just take the easy way out and make them 6 or 8 inches longer and let them puddle a little bit. Saves them from looking like they were ordered from Penney's or something equally grizzly. (grin) Don't forget the RETURN (where the drape returns to the wall and wraps around the bracket). Usually brackets have a place to take a hook for this purpose, but if not, an eye hook set into the wall will do nicely. Makes your installation look totally finished and professional, too. One more tip? When you've hung your drapes open them fully, and then pleat them by and. Tie scraps of fabric around the pleated drape to hold it in place and let it sit for about 2 weeks or longer. (Longer is better.) The pleats will be smooth, gentle and never fall out! Fabric has a "memory" and when set this way, only the pleats and folds you've put there will forever be remembered. This is how a 'pro' finishes their installation. (Sadly, most customers are too anxious to use the drape to wait the two weeks. We throw in Roller Shades with every drapery order, so they can have privacy while letting their new drapes "set" and "take" the perfect pleating. We charge a whole lot for this little trick, but be my guest. It works better than steam pressing them in place! Honest!!