As any interior decorator will tell you, curtains can make a room—or break one! So it's important to choose them carefully. You'll need to consider colour and fabric, length and width, whether you want them lined or unlined, and then make a decision on whether to look for a custom-made or an off-the-shelf pair. Apart from aesthetics, you'll need to think about what function you want your curtains to fulfill. Do you need a heavy pair to shade a sunny room? Or something lighter, that will let a breeze and some light through?
The first thing to do, when buying curtains, is to decide how high above the window you want the curtains to sit. You'll want them to hang about halfway between the top of the window and the ceiling. For lower ceilings, push the rod up higher, to create an illusion of height. Next, you'll need to decide whether you want your curtains to just skim the floor, or whether you want to go for a slightly romantic, 'puddle' effect, where the curtains flow out onto the floor. Once you've decided on where the rod is going to go, and where you want the ends of your curtains to sit, get the tape measure out and get to work measuring.
You can choose any fabric you please for your curtains, but keep you needs in mind. Lighter fabrics will obviously let more light through, while heavier fabrics will keep out sun and heat. Whether to line your curtains is, again, down to your own needs, but lining them will add to their fulness, giving a more voluptuous feel. On the other side of the coin, if you want a romantic, floaty effect, go for a light fabric like voile and leave them unlined.
Next, you'll need to measure the width of your window. The rod you choose should be 7-9cm wider than the window frame so you don't block too much glass when the curtains are open. The width of curtain fabric you need will depend on the fabric you choose—for lighter fabrics, go for 2 to 3 times the total width of the rod; for heavier fabrics twice the width of the rod should be sufficient. The curtain fabric needs to be this wide so you'll have a nice drape and concetina effect. If you need to block out the sun, extra width around the perimeter of your window frame will block out any light that might try to sneak in around the edges.
We can see a lovely example of a 'puddle' effect in these blue ombre drapes by Lovely Home Idea.
As a rule of thumb: if you have strong patterns on furniture or bedding, it's best to stick with curtains in solid colour-blocks. On the flip-side, if your furniture and soft furnishings are mostly in blocks of colour then go for pattered curtains. If you're going for patterned curtains, small prints—dots or lines, for example—are an easy way to do it, and the pattern will add texture to the room. If you're daring, and sure of what you're doing, a large, graphic print can be absolutely spectacular.
Inevitably, sunlight will fade the patterns and colours on curtain fabric over time. If your room is very sunny, it's a good idea to stay away from bright colors, since they will fade faster. Neutrals—whether in a colour or a pattern—won't fade as quickly. However, if you're the kind of person who likes to redecorate fairly frequently, you don't have to worry so much about fading.