Payment: I normally consider hourly rate (payment/hours), purpose (is it commercial/a friend/charity/...), do I get anything else (publicity, fun, ...), commercial market price for similar tasks (which of course is the difficult thing to get to know; I would say much more than 15$), skills (how competent are you?), craft or art (unique art is more expensive). You get pay for the job, not for the hours, which means a) hourly rate is for your own check of what you earn, and b) skills/competence is not about how fast you diagram, but at what quality you do it.
Shading/3D: Black~Terror writes:
except where can I shade? The diagrams shown all are "supposed" to be flat, and shading's for if the model's 3-D, right
Diagrams are not supposed to be flat. Try to fold in anything but foil, and you will see that flaps rise a bit enabling you to see the layers, in particular if you look at them at a slight angle. Also, seeing the layers makes it clearer to the reader what goes on.
Dinogami's example is good. You can also see one of mine: http://papirfoldning.dk/temp/sommerfugl-a.svg
which was made for a womens' magazine. Layers are shown by distorting the layer edges a bit, and gradients suggest some 3D-shading. I do not try to maintain a correct drawing perspective or a consistent light source, the aim is make the instructions clearer and the drawings more pleasing to look at.
The above was what I delivered - the magazine did their own layout of the drawings, and for some reason retyped the texts introducing a couple of weird errors. I believe this is a common situation which I try to counter by offering to make a proof reading myself.
Inkscape gradients: Select the polygon. Type ctrl-shift-F which will open the fill-and-lines dialog. In the first tab you can choose no fill/color/linear gradient/radial gradient/patterns. You can edit the gradients, e.g. inserting more stops. Switching linear/radial gradients does not change the gradient definitions, only how they are applied. I you copy/paste an object, the gradient will be copied, duplicate will not. Probably you'll want to uncheck "Prevent sharing of gradient definitions" in Inkscape settings/miscellaneous.
Font: Serif fonts are said provide better readability for body text, whereas non-serif fonts are better for small or low-resolution text. The latter is the reason why sans-serif has been popular for digital media: monitors traditionally have an inferior resolution. However, this situation is improving, so today the choice can be made more freely according to aesthetics and size. For origami instructions I normally use a sans-serif font, and, for portability, often a standard font, unless I know I will send bitmaps only.



