There are a few things you need to know about diagramming:

1) How to draw a diagram.
2) Symbols to use.
3) Grammer.
4) How to make things clear to the reader.
5) (you may like to do this) How publish your diagrams.

I would explain points 1 and 5. for points 2-4, they are covered in the page called "Diagramming (by Robert Lang)"

Point 1:
You could draw diagrams either by hand or using a computer. If the models are hand-drawn, they must be clear, and not too complex. (Plus, no one could draw diagrams for complex models by hand only.) If you are using a computer, you should use the following softwares:

Adobe Illustrator
Inkscape
Origami Simulation (a program made by Robert Lang.

It would be good if you have a vector drawing program.
If you are new to diagramming, you should refer to books for ideas, and finish reading all the infomation available on the website.

Point 5:
If you have enough diagrams, you should publish a book. However, if you only have a few, or could not affrod publishing one, you could submit them to an origami society. Here are some suggestions:

OrigamiUSA
British Origami Society
Japan Origami Academic Sociey
Creased Magazine

The first three are origami societies. They publish magazines for members, and conduct origami workshops. You could grant them permission on how you want your diagrams could be used.

Permission form for BOS: http://www.britishorigami.info/society/magazine.php
Permission form for OrigamiUSA: http://www.origami-usa.org/files/Permission_Form_20070722_0.pdf

As for the Creased Magazine, I would not reccomend submitting diagrams to them, as you would be giving them exclusive permission.