1. Not Measuring Correctly
The first thing you should do is measure your windows and make adjustments depending on how you want to hang the window treatments. It will save you another trip to the store if your curtains and rods are the right size.
2. Hanging Curtains Too Low
Hang curtain rods and draperies at the ceiling to make the room feel taller — this is especially important in small spaces.
3. Buying Curtains That Are Too Short
For classic side panels, you really have to go all the way to the floor. If you're looking at ready-made drapes, make sure that they touch the floor, even if you have to buy the next size up and have them hemmed.
4. Not Thinking About Fullness
Traditionally, you should be looking at 2 to 2½ times the width of the window for the fullness of the drapes. So if your window is 4 feet wide, the ungathered panels should be at least 8 feet wide, or even better, 10 feet.
5. Avoiding the Iron
Wrinkled curtains look messy. Don't be lazy and think they somehow will become unwrinkled after a few days, steam or iron them before you hang them.
6. Forgetting About Hardware
The window treatments are the main event, but the hardware is important, too. Pay attention to how heavy the curtains are, sometimes you may need a rod with extra support or added hardware. Also, think about the style of the rod and finial and how it goes with the curtain style.