Clone techniques. One of the most common tools of a shinobi. We're here today to try and find out how they work.

A clone has two basic parts. A chakra exterior, and a substance or medium inside that.

Clone Technique. The basic, academy-level jutsu. This jutsu forms a human outline out of chakra. As there is no inner material giving it substance, it is insubstantial. Can't hit things, because there is no solid substance to hit with.

Shadow Clone Technique. Our favorite technique to spam. This jutsu is so chakra-intensive because besides the outline of chakra, it forces the user to fill the entire outline with just chakra. However, it can strike as hard as the user, with the limitation that if the chakra coating is pierced, it deflates like a balloon.

Water Clone Technique. The first elemental one. Here, the outline of the clone is filled with water. Not water chakra, just water. This technique basically creates person-sized dummies of animated water. Due to this, they are much weaker than the original, but cost much less chakra.

Lightning Release Shadow Clone. Kakashi's technique. This one, as a derivative of the Shadow Clone Technique, fills the clone entirely with chakra. However, this chakra underwent nature transformations, so the clone is filled with Lightning Release chakra. When it deflates, it releases all the chakra in a rush of electricity, forming its greatest weakness (its fragility) into an attack.

Crow Clone Technique. Itachi's technique. I don't get this one, and please don't ask. I don't want to think about how he forces crows into the shape of a person. //cringe

But anyway, since it uses crows as a medium, it requires less chakra than a Shadow Clone. It's the only real summon clone I can think of.

Sand Clone. Gaara's technique, and an interesting case. Gaara uses chakra to form a body out of sand, similar to the Water Clone Technique. It is a fairly generic technique normally. But, in this case, Gaara also controls the sand. So when the clone is dispersed, Gaara can control the sand to reform it or use it as an attack. Or even hide things inside it, as is shown when he hides Gold Dust inside a clone against the Second Mizukage.

For creating a clone technique, there are two main options. Using a natural medium or some form of chakra. 

If it's a medium of some sort, like rocks, it'd just be a Rock Clone.

If it's elemental chakra, like Wind Release, it'd be a Wind Release Shadow Clone.

Hope this helps. Mizukage out.