I learned how to make this heart when I was about 10-years-old. :) I thought it was common for people to know how to fold this kind of heart, but my friends are always in awe every time I make one.
Please remember that when folding money, you should crease it with a lot of pressure and precisely as possible!
Sorry if the instructions are a little difficult to follow. I don't really know all the origami terms. ;=__= But the pictures should give you an idea of how to follow along.
Start with a crisp dollar.
Crease the dollar up into a point, like the way you would make a paper airplane. xP
Crease it down.
Unfold and use the new guidelines and push in the sides.
It should become a triangle shape and look like a house.
Next, fold the flaps up the point.
Stick you finger in the new flap.
And squish it down to make a square.
Repeat on the other side.
Then, using this picture as a guide, fold the corners of the square toward the center, where the crease is.
If you have big fingers like me...;-__-
Use a pen to squeeze in-between the new flaps and press down.
<---It should look like this. It may be a little difficult at first because it's so small, but after making these hearts for a while, it should become fairly easy.
Then, do the exact same on the other side. By now, you probably just want to get this over with.
Fold the dollar like so.
Them pull it over to meet the other side. This will hide the extra space.
Hide the extra bits of dollar by tucking it under the main shape.
<--Fold the flappy part of the dollar to the other point.
You can stop here if you want.
But I fold in the points so that it looks like an evenly-rounded heart.