This is the base of a great many models, and can be used for more than making the famous origami crane, where it gets its name.

Supplies

Just a square sheet of paper

Step 1: The Base of the Base

Crease in half (fold sharply and unfold) in half, in a triangle shape as shown. Flip the paper over and fold one side inward along the crease as shown. Repeat with the other side.

Step 2: The Petal Fold

This is the trickiest part; you are going to take the two side flaps and fold them diagonally to the middle as shown, and fold the top "flap" over them, also as shown. Use these creases to open and flatten the inner pocket, creating a large narrow rhombus. Repeat this on the other side.

Please do let me know if this was at all helpful.