The origami heart is a classic for a reason: one square sheet, eight folds, and you have a clean little paper heart to slip into a card, tape on a fridge or hand to someone on Valentine's Day. Start colour side down - the white side ends up forming the inner detail.
This walkthrough from EzOrigami breaks it into eight clear steps. The only fiddly moment is the squash fold around step seven. Once that clicks you will be turning them out by the dozen.
What paper to use for a paper heart
Any square will fold, but the paper decides how sharp the finished heart looks. Standard 15 cm origami paper gives a heart about 7 cm across, which is the right size for a card. Thinner paper takes a crisper crease and is more forgiving through the squash fold; thick scrapbook card fights you at the layered stages and the point ends up blunt.
Duo paper - coloured on both sides - is worth seeking out here, because the reverse shows through on the two lobes at the top. A red-and-white or red-and-pink sheet does the work for you without a single extra fold.
Getting a clean point at the bottom
The bottom point is what makes a heart read as a heart rather than a blob. Two things cause a soft one. First, an inaccurate first diagonal - if that crease is off by a couple of millimetres, every fold after it inherits the error. Second, not pressing hard enough. Run a thumbnail or a bone folder along each crease before moving on.
If your heart will not sit flat, the culprit is almost always the squash fold being pushed out of square. Open it back to the previous step and redo it rather than trying to flatten it into submission.
What to do with them
A single paper heart glued to a folded card is the obvious use. Beyond that: thread a dozen on cotton for a garland, fold them small from used book pages for a rustic look, or write a note on the square before you start folding so the message hides inside. Fold one from a banknote and it becomes a gift in itself.
The same shape works on a banknote, and it turns a plain cash gift into something worth keeping. How to fold money into a heart walks through the dollar-bill version.