Origami is the ancient Japanese art of paper folding. Traditional designs start with a square piece of plain paper. This may be of uniform colour or coloured one side and not the other. The model should be constructed using only clean folds. Good origami paper is both thin and strong.
Modern designs or non-Japanese designs sometimes use non-square paper. For example the "traditional" English sailing boat and plane models may be made from a rectangle. The creation of these presumably results from the greater availability of foolscap and then A4 sizes once paper was no longer always hand-made. There are even a few designs that start from triangular or hexagonal paper. These shapes can be derived from square or rectangular paper though.
Some paper-folders use patterned paper, or discrete markings to produce a model. I regard this as OK when it is merely an enhancement, but cheating if the model only works with such special paper.
Other folders allow cuts to be made in the paper. This may be simply to avoid an extra level of folding. However, normally paper cutting is a totally different art form.
Portrait origami often uses modelling of the paper rather than clean folds. This is less predictable and more personal than pure origami.
Multiple pieces of paper may be used in models. This is best if each piece makes a discrete model that then works with the others. One good example of this is Aladdin's lamp, where the lamp and genie are formed separately but can be fitted together. This is another origami extension where enhancement is good but necessity is bad.
Some folders use materials other than paper, eg foil or net fabric. This can be effective but should not be essential to an origami model.
Some origami models are essentially flat 2-dimensional representations of an object. My personal preference is for 3-dimensional models. They are even better if they have a use and more fun if they move in some way!
Fold one corner across to find the amount of paper that isn't needed.
Either cut carefully using the triangle's edge as a guide or fold the remnant back along this edge first to act as a cutting guide.
Unfold the square that is left. Most origami models will require this first diagonal fold anyway.
