Let's discuss purely technical details of icon making
1. Lines, angles
One of the most important parts of the image is the outline of the object, i.e. solid linear marking, which limits the object from the rest of the image. When creating large-scale images, the designer rarely cares about highlighting of objects with additional lines. This is not needed because of the scale: even non-contrasted objects do not blur into a one. Icon graphics is different. Two variants are possible: either foreground and background colors have to be from opposite sides of the color chart, or the foreground must be separated from the background by contrast lines and shadows. I will dwell on lines deeper.
If we return more to the large scale images, we can note that in order to highlight edges, we can use any (including the most complex) angles, Bezier curves and edges. Anyway, the line will look perfect due to anti-aliasing. When decreasing the graphic scale to the small icon size, situation changes greatly. When every single pixel is equally important and can ruin the overall appearance of the icon, anti-aliasing is simply not applicable. It comes that you have to think about the possible line angles.
The slope you choose for the line, determines the step of this line. Because every line consists of primary elements, the combination of which determines its accuracy and visual appeal.
For instance, a 18-degree angle consists of many small 3-pixel lines connected using a 1-pixel downshift:
This is how nearly each line looks like. Primary element followed by joining followed by second primary element. Unfortunately, not every slope creates lines that look look neet and not messy.
For example, look at 25 and 20-degree angles:
It can be easily known which line is more attractive. The 25-degree angle makes a line containing even 2-pixel basic elements. The 20-degree slope has a basic element consisting of three lines: 3-pixel, 3-pixel and 2-pixel. The slope is more complex, thus, if not supported by additional visual effects, it brings a feeling of messiness: the basic elements have contrast which is too strong to hide from the human sight.
Here we can see the first rule. The most "correct" angles must make as plain primary elements as possible. Thus, the ideal angles are 0 and 90 degrees. In them, 1-pixel basic elements are joined without any shift and form smooth lines. Less ideal are slopes which form primary elements of 1, 2, 3 pixel with 1-pixel downshift. Surely, the lines will not be smooth, but the human sight will process the picture and provide to the user what you meant to show to him. Also, the mentioned angles can be considered acceptable (but at a stretch): slopes with basic elements consisting of unequal lines shifted by more than 1 pixel.
Now we can touch another problem. In the last paragraph, I purposely defined angles with primary elements of 1, 2 and 3 pixels as correct. Such small lines, especially when a large number of them is combined, appear as solid. But what happens if we increase the primary elements to 10 or 20 pixels?
Here is an example:
It can be clearly noticed that the line doesn't have solidness. It is not a single line anymore; it is a combination of several lines, located near one another. Rarely any designer wants its creation to look that way. So, we have another rule: if you use small angles, which make long primary elements, it has to be justified and used with maximum attention.
And, finally, the last aspect I wanted to tell about lines. I already wrote that the basic element has to be as simple as it can.
For example, a 25-degree slope can be produced in the two (of course more of them exists) following ways:
In the first case the basic element is a 2-pixel line. In the second picture, it is made of three lines: 3-pixel, 2-pixel and 1-pixel. The same angle but the look is different. The complex primary element made the line untidy.
Such examples can be made for about any slope, so in your works, make sure to simplify as much as possible.
It can be stated without an exaggeration that the color is the leading aspect of your work; improper or badly balanced colors can kill even the best idea. What can we say about the color in miniature graphics?
First, there is a certain rule: if the image looks poor when converted to monochrome, then the colors that were used are incorrect. This rule is true not exclusively for icons but for the whole graphic design.
Second, you will be unable to apply safe RGB. Sure, you can select GIF colors only, but this ties you hand and foot. Gradients, shadows, blending and many other tricks will not be available to you.
Third, try to enlarge the areas of "plain" color. The more consistently colored parts without blurring and jumps your composition has, the more neat it appears. Pictograms are too tiny and the excess usage of complex filters makes the image look dirty.
Fourth, gradients. This is a wonderful tool which can change the look of any composition. Other than visuals, gradients are an ideal way to abolish the "broken line" look (lines with too long primary elements). But be careful when applying them since too much gradients can kill the flat color, and be unable to fit into the gif palette.
Fifth, shadows and highlights. All rules for using shades and flares in icon creation are completely the same to the aspects of the general graphic design. The only thing I have to note: draw everything yourself. Don't use filters, make all shades and highlights in a different layer and after that edit the opacity. When applying filters, you almost never can predict what the result will be. It is bad when you don't control the making of a project. It is worse if you don't control it if drawing icons.
And, lastly, sixth. Nuancing is the main aspect of pictogram design, which largely affects the esthetic appearance of the composition. If the green human eye in the image is sized 1 pixel, increase the color saturation. For example, instead of 0, 131, 159 make 71, 195, 242. It doesn't matter that the human eye never has such color; in the first example it will appear like a gray dot, and in the second case it will definitely be a green eye.
completely control the picture, do not allow the visual illusions to spoil your work. It is acceptable if something is not consistent from the technical point of view, but the whole picture must be perfect.
As an example, I pictured the packet of juice located before me. The image has plain color, gradients with broken lines, shades and flares and tints.
If I wrote about something bigger than pictogram design, this chapter wouldn't fit into a whole book, but the size of compositions restricts fonts too.
The size of symbols becomes the main aspect as opposed to their look. Almost in any case, unless the letters are the primary part of the project, the text size must be reduced to the greatest extent possible.
In principle, virtually any graphic company has its own font with tiny characters. Such a font can be created in a couple of hours. You can browse the web and collect your own library of very interesting fonts. Primarily, I advice you to get the DS Pixel and Seventen 7Vedi website and the complete series of fonts from the Lakmus Lab website.
If you don't need a new font, small typesizes of Arial and Verdana may do. As a last resort, you can create the needed characters by hand.
There are not many rules there. First, letters cannot be less than 5 pixels high or less than 3 pixels wide.
Second, letters should not use anti-aliasing. It turns the font into an incomprehensible mixture of pixels.
However, there are no rules without exceptions and the 5-point Arial looks perfectly understandable.