Where Do I Start?

Set aside style considerations for a moment; function comes first and will limit your curtain choices, in a good way. If you want treatments that provide privacy or total darkness, you need lined curtains. If you’re OK with light filtering through or if your curtains are simply decorative, unlined will work. Lining is more expensive but has other advantages: It can shield fabric from sun damage, making curtains last longer. A lining also adds heft, which protects against drafts and helps fabric fall more luxuriously. For maximum durability, light blockage, body, and insulation, you can get curtains with an interlining, too—a layer of flannel-like fabric sewn between the lining and the “face” fabric. This is a common option for custom-made curtains but not widely available in less expensive ready-made panels.

What About Fabric and Color?

Texture

Consider the mood of the room. For a formal space, there’s heavy silk or velvet (a great insulator); both are dry-clean only. More practical (often washable) options include silky rayon blends and cotton sateen. For a casual feel, there are billowy linen (generally dry-clean only) and crinkly crushed velvet. Cotton and cotton blends work with any type of decor and bring a crisp, neat feel, as does seasonless wool or wool blends.

Color

You’ll need to decide if you want the curtains to blend with the decor or to pop. For blending, pick curtains that are the same tone as the wall but a few shades darker, or choose a non-dominant subtle color in the room (a soft shade from the rug, say). A bold color will work like an exclamation point (if you’re looking to add some wow). Also keep in mind that in a space where the sun shines through unlined curtains, the color will infuse the room. Blue can be eerie; pink, cheery.

Prints and Patterns

A rule of thumb: If you have patterned furniture or bedding (or a very elaborate rug), stick with solid curtains. If you have solid-color furniture or bedding, consider patterned curtains. For a subtle hit of style and energy, go for a small, neutral print, like dots or paisley, which reads like texture from afar. A large, graphic print in a color that relates to the existing decor is daring but can be spectacular.

How Long Should Curtains Be?

Floor-length is the way to go, unless there’s a radiator or a deep sill in the way. Ready-made panels are available in lengths from 63 to 144 inches. Measure from the floor to where you’ll hang the rod, then round up. You can always have the dry cleaner hem them a bit if needed. You’ll get the most current look if the fabric makes contact with the floor (or sill or radiator). Too-short curtains can seem nerdy and off, like high-waters. Here are two surefire approaches.

Just Hitting the Floor or Sill

This look is classic and tailored; it makes sense if you’ll be opening and closing the curtains a lot (they’ll easily fall back into place every time you move them). The fabric should just touch the floor or hover half an inch above. This is also a great approach for café curtains (short panels that cover only the lower portion of a window and hit the sill), which work well in spots like the kitchen and bathroom, where long drapes aren’t practical.

Breaking Slightly at the Floor

Panels that extend onto the floor by one to three inches are the most stylish right now. They’re more relaxed than those that graze the floor (left), but they still feel tailored—think of a pair of dress trousers. If you have uneven floors or are worried about precision measuring, this style is more forgiving. In formal rooms, an exaggerated take—six or so inches of fabric pooling on the floor—can look romantic but is also high-maintenance; curtains need refluffing every time you vacuum or the cat lies on them.