A question I often get asked and, when I was younger, wanted to ask, is "how did you fold that?" I find this a hard question to answer because for me, origami is an art that is difficult to understand without actually picking up a piece of paper, folding it, and seeing the results.
However, I will try to describe some of my process here. Although there are many details involved in the creation of an origami model I will not cover, this should give you a good general idea of how it all works.
Generally speaking, most origami models are folded one of three ways: by following some kind of sequence that takes the piece of paper and builds up the model fold by fold, by collapsing a crease pattern, a drawing that shows all of the most important creases in the model, or by trial and error.
Pretty much all of my models are made from crease patterns or CPs. A crease pattern is a diagram representing all of the folds used in the creation of a model’s basic structure. Each line represents a fold, one color signifying mountain (away from the viewer) folds and the other color signifying valley (toward the viewer) folds.
This is because I plan out all of the creases in the model before I fold it in a CP, using design methods that allow the me to accurately predict and control the what the final model will look like.
Once the design process is finished and I decide to fold an origami figure, the first thing I do after cutting the paper square is start finding reference points for the most important creases. There are a few methods of doing this: Trial and error, using a computer program like Robert Lang's Reference Finder, or measuring and marking, which consists of finding the reference point on the CP, multiplying the coordinates to fit your paper size, and drawing them where they are needed. I use some of all of these.
After I have found the most important reference points, I start reproducing all of the creases in the CP on my paper one at a time. This process can last quite a few hours, but depends completely on how complex the model is and it's corresponding CP. After I have finished the pre-creasing, as it is called, I proceed to "collapse" the crease pattern. This consists of folding along all of the creases in the paper and making the necessary adjustments for the model to lie flat. This is much easier said than done: it takes a lot of practice to master this step.