The following "instructable" will be your step-by-step guide to making the ever-essential Dollar Origami Heart. It's not easy, and it's often tedious, but it's worth it. Once you get it, you'll never forget it (and then you can teach it too)! Enjoy!
Step 1: Fold Corners to Create Creases
Start by taking your first corner and fold down (or up). When you fold down your corner, make sure to run your finger nail along the fold to create a crease in the dollar bill. Unfold the corner and repeat on opposing corner, being sure to run your finger along each fold to ensure a good crease.
Step 2: Unfold and Ensure Your Creases Have Created an X
After folding each corner down, solidifying the fold and unfolding again, you have created an X at either side of your dollar bill.
Step 3: Pinch Bill to Create Triangle
You now want to take the dollar bill and pinch the top sides where you have created the X on your bill (on both ends). Pinch as shown in the picture.
Step 4: Create a Triangle at the End of the Bill
By pinching and the folding the pinch, you should have created a triangle, like the one in this photo.
Step 5: Create a Triangle at the Other End of the Bill
Follow previous step for both sides of the bill, end result should look like this. Again, be sure you have run your finger nail along the fold to secure the fold.
Step 6: Fold 4 More Corners
At this point you want to take your 4 free corners (2 of them on the left side are circled in yellow as well as the one in the top right) and fold them up to the tip of the triangle (tip of the triangle is circled in red on either side). As you can see, my bottom right corner is already folded to the tip of its triangle.
Step 7: Secure Folds
By now, all for corners of the 2 triangles should be folded, you want to secure the folds by running your finger nail (or a coin would work too) along the fold.
Step 8: Pull Folds Apart to Create Square
Stick your finger (this is the easiest way, or you can push on the fold) in between the smaller triangle you have made. After your push your finger in to create space, remove finger and push down the fold (circle in red) to the base to turn the triangle into a folded square by bringing the tip (red circle) in towards Washington's face.
Step 9: Pushing Down the Square
Here you can see how to push the triangle down to create a square. Make sure to line the crease of the triangle to the corner close to Washington's face.
Step 10: Create Your Square
The finished product of turning the triangle into a square. Repeat 3 more times for each triangle.
Step 11: Secure Your 4 Squares
You should now have 4 squares made from pushing down the triangles. The fold of the square should be reinforced again using your nail or a coin to secure folds.
Step 12: 8 More Triangles
Let's make more triangles! (as if you weren't sick of geometry and small folds by now...) Take the 2 free corners (example in red circle) from each of your 4 squares and fold them in, lining up (green line example) with the center line (blue line example) on your square. You should create 8 triangles from your 4 squares. The second picture is an example of what one of the sides of your dollar bill should look like after the folds.
Step 13: Push Down the Folds
Here is where it gets slightly tricky. You want to stick your finger in the triangle until you have opened it slightly, just enough to push the top (the red circle example) of the triangle down. Similar to the method we used from turning the 4 squares into 8 triangles except you're just folding the tip down. You can see in the first image my finger pushing the fold down to create yet another, smaller triangle. The second image shows what it should look like. Do this to all 8 triangles.
Step 14: Check to Ensure All Angles Are Even and All Folds Are Secure
Again, take this time to run your fingernail or coin along folds or push down the tiny triangle folds you have just made. Your dollar bill should now look like this.
Step 15: Cover Up Washington's Face
Bring either side of your dollar bill together. You will need to fold one side in by lining up the straight lines and folding underneath one side of the dollar bill.
Step 16: Rejoice! You're Almost Done!
You should now have a large diamond shaped dollar bill with your (seemingly 456,000) triangles and what should look sort of like a snowflake/sunburst in the middle. Secure all folds (again, ugh). But rejoice, you're almost done!
Step 17: Fold Down the Top
Fold down the top of your dollar bill backward, so that the (sunburst, snowflake) is still visible on the front. The top should now be taking the shape of the heart.
Step 18: Seriously, You're So Close!
Take the extra little bottom piece on the right (the part in the circle, that my finger is sort of covering) and fold it under so that it's not showing. You can just take the little piece and fold it in so that it is secured between the back and the front, make sure no piece of it shows.
Step 19: Take a Breather, It Finally Looks Like a Heart!
You're so close and you're probably feeling better about your efforts, because now it's finally starting to take shape. By this point it should look a lot like a heart. But we still have a few more steps!
Step 20: Fold in the Corners to Round the Heart Shape
Fold in the 2 sharp corners of the heart to round them off. Making sure you make only one fold, and that it is a nice parallel line with the center line.
Step 21: It's a Heart!
You're almost there...but take a minute and enjoy your work...
Step 22: Secure All Folds...and Then Secure Them Again!
At this point, you've put in way too much effort to not trace over ever fold with your finger nail and/or something that will secure the folds. I use my fingernails, and sometimes roll a cup over top of the entire thing just to smash all folds and creases into place.
Step 23: Add a Quarter If You Want!
You did it! Now to add the quarter if you want because, why not?
This is the step where I usually tell people -- don't do it unless you want to, I think the heart without the quarter looks just as cool.
Take the free corners of your (sunburst, snowflake) and pull them up. This is easiest to do by sticking a finger underneath them. Now to wedge the quarter in there, ensuring that all free corners of the (sunburst, snowflake) are securing and holding down the quarter.
Step 24: Congratulations -- You've Given Money a Heart!
You finally did it! Origami is tedious and sometimes frustrating, but always worthwhile. I didn't get the dollar/heart origami on my first try, but once I did get it I never forgot how to do it. I promise you, once you get it down you won't be able to forget it! And then you can pass it on to other people. Congrats -- I hope you enjoyed!