1. Distance between the ceiling and top of the window;
2. Height of the top of the window to floor;
3. Width of the window;
4. Distance from the side of the window to the end of wall/window on each side.
To get a proper curtain length, you'll expect to hang the rod 4" down from ceiling in a standard (8 or 9ft) room. Taller ones should be 6-10" above the top of window. A 96" curtain length should be the go to for 8ft.
For the rod width, add 12"-20" to the window width measurement you jotted down. This will ensure the rod is long enough to extend 10" past the window frame.
Buy Enough Panels
A standard curtain panel is 50"-54". If you want to close the curtains you will need to cover 2x the width of the window. You will likely need more than 2 panels for each window.
If you want a fuller, formal look, you will want to add additional panels as well. If your only goal is to flank the window, one panel on each side should be fine so long as the scale of the room is moderate.
DO: Remember to hang them outside the window molding to accentuate your window. Extend your rod anywhere form 6" to 12" beyond the window frame on each side.
What's The Best Color & Style For The Room?
Feel Of The Room
What type of room are you buying curtains for? Is the room formal? Choose a traditional pattern like a greek key trim on a solid white or a velvet or silk in a solid color.
Is the room warm and relaxed? If you are going for the over stuffed comfortable room with neutral colors, choose linen curtain panels.
Is the room playful or you are looking to add a pop of color? Is it a powder room? I recommend installing a roman shade. It provides privacy, but can still add a decorative to the room.
Fell Of The Room
What type of room are you buying curtains for? Is the room formal? Is the room warm and relaxed? Is the room playful or you are looking to add a pop of color? Is it a powder room? If you are going for the over stuffed comfortable room with neutral colors, choose linen curtain panels.
First consider what problem you want to solve with curtains? Is this a primarily decorative decision or do you need to modify the light entering the room?
Do you want to block light & add privacy? You'll want lined curtains or a thick fabric and enough panels to cover the entire window.
Do you need to filter light, but keep the room bright? Choose a pair that will add texture to the room but can be stationary.