Let's consider strictly technical aspects of icon making
1. Lines, angles
One of the vital elements of the composition is the framework of the object, i.e. rough linear marking, which separates the object from the background. When creating normal-sized graphics, the designer occasionally thinks about defining objects with complementary outlines. This is unnecessary because of the scale: even low contrast objects do not mix into a single whole. Pixel graphics is different. Two solutions are possible: either object and background colors have to be from opposite sides of the color chart, or the object should be separated from the background by visible lines and shadows. I would like to dwell on lines in more detail.
If we return again to the large scale graphics, we see that in order to highlight contours, we can use any (even the most complicated) angles, Bezier curves and borders. In any case, the line will look ideal due to anti-aliasing. When decreasing the image dimensions to the small icon size, situation changes greatly. When each single pixel is vitally valuable and can ruin the whole appearance of the composition, anti-aliasing is just not applicable. It means that you should consider the possible line slopes.
The slope you select for the line, determines the step of this line. This means that every line is made of primary elements, the combination of which determines its neatness and esthetics.
For example, a 18-degree angle consists of many small 3-pixel lines connected using a 1-pixel downshift:
This is how nearly every line looks like. Primary element with joining and another primary element. Unfortunately, not every angle makes the line look attractive and not annoying.
For example, here are 25 and 20-degree slopes:
It can be easily seen which line is more appealing. The 25-degree angle makes a line containing even 2-pixel basic elements. The 20-degree angle has a primary element containing of three parts: 3-pixel, 3-pixel and 2-pixel. The slope is more complex, therefore, when not combined by additional visual effects, it creates 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 conclusion. The most "correct" slopes have to make as plain basic elements as they can. therefore, the perfect angles are 0 and 90 degrees. In those, 1-pixel primary elements are combined without any shift and produce even lines. Less perfect are angles which form basic elements of 1, 2, 3 pixel with 1-pixel downshift. Of course, the lines can not be even, but the human brain will process the picture and present to the user what you meant to show to him. Also, the following angles can be considered acceptable (but at a stretch): angles with basic elements made of different lines shifted by more than 1 pixel.
Now we can touch another issue. In the previous paragraph, I purposely defined angles with basic elements of 1, 2 and 3 pixels as correct. Such tiny lines, especially when a large number of them is combined, appear as a single whole. But what do we see if we increase the basic elements to 10 or 20 pixels?
Here is an example:
It can be clearly seen that the line doesn't have integrity. It is not a single line now; it is a combination of different lines, located near each other. Hardly any designer wants its creation to look that way. Thus, we have another conclusion: if you use minimal angles, which produse long basic elements, it has to be reasoned and used with great attention.
And, finally, the last aspect I wanted to tell about lines. I already wrote that the primary element has to be as plain as possible.
For instance, a 25-degree angle can be drawn in the two (sure more of them exists) following ways:
In the first picture the primary 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 image is different. The complex basic element made the line untidy.
Such examples can be produced for almost any slope, so in your works, try to simplify everything.
It can be said without an overstatement that the color is the leading aspect of your work; improper or poorly matched colors can kill even the most creative idea. What can we write about the color in miniature graphics?
First, there is a certain rule: if the picture looks poor when reduced to monochrome, it means the colors that were used are incorrect. This rule is valid not only for icons but for the entire graphic design.
Second, you will probably unable to use common RGB. Of course, you can select GIF colors only, but this ties you hand and foot. Gradients, shadows, blending and many other effects will not be available to you.
Third, try to increase the portion of "flat" color. The more evenly colored parts without blurring and jumps your picture has, the more clear it appears. Pictograms are too tiny and the excess usage of special effects makes the image look dirty.
Fourth, gradients. This is a great instrument which can improve the look of any project. Besides visuals, gradients are an ideal solution to get rid of the "broken line" look (lines with too long primary elements). But be careful when using them since too many gradients can kill the plain color, and be not suitable for the gif palette.
Fifth, shadows and flares. All rules for using shades and highlights in icon making are completely identical to the aspects of the overall graphic design. The only ine I have to mention: create everything yourself. Don't apply effects, make all shades and flares in a different layer and after that edit its transparency. When applying effects, you rarely know what the result will be. It is unfavorable when you can't control the making of a project. It is worse if you don't control it when creating miniatures.
And, lastly, sixth. Tinting is the main detail of icon design, which greatly results the esthetic appearance of the project. When the blue human eye in the picture has the size of 1 pixel, increase the color saturation. For instance, instead of 0, 131, 159 choose 71, 195, 242. It is indifferent that the human eye never has such color; in the first case it will look like a gray dot, but in the second one it will definitely be a blue eye.
Thoroughly control the picture, do not allow the optical illusions to spoil your work. It is acceptable if objects is not consistent from the technical point of view, but the whole picture must be perfect.
As an example, I drew the pack of juice located before me. The picture has flat color, gradients with broken lines, shadows and highlights and tints.
If I talked about something other than icon creation, this part wouldn't fit into an entire book, but the resolution of compositions restricts fonts too.
The size of symbols is the leading issue as opposed to their look. Nearly in all cases, unless the letters are the main part of the image, the text size has to be reduced to the largest extent possible.
In general, almost any graphic company has its unique font with tiny letters. Such a font can be crafted in a few hours. You can browse the web and make your own library of very nice fonts. First of all, I advice you to get the DS Pixel and Seventen 7Vedi website as well as the whole series of fonts from the Lakmus Lab website.
If you don't want a new font, little sizes of Arial and Verdana may do. As a last resort, you can draw the needed letters by hand.
There are quite a few 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 appears rather readable.