BASIC WINDOW STAR

Start with a square. My tissue paper has a slight curl to it; this does not affect the outcome. You can use any size square for this project.
Fold that square in half, and crease the fold.
Slip your really sharp knife in the fold and gently cut.
Fold the resulting rectangles you have in half, crease, and cut.
You should have four small squares now. Fold those in half, crease, and cut.
That's all the cutting, your paper is ready to be folded!
Fold your small rectangles in half, long-ways.
Fold the corners to the center.
On one end, make a second fold to the middle. Make sure you are still creasing. (sorry for the blurry photo!)
Do that seven more times. You need eight in all. Time to glue!
Position them along their creases thusly, and glue together.
Continue till you have all eight there. Tuck the last diamond under the edge of the first, and glue them together.
There is your finished window star! Go hang it up!