Let's consider strictly technical details of icon creation
1. Lines, angles
One of the vital parts of the image is the outline of the object, i.e. rough line, which limits the object from the rest of the image. When creating normal-sized images, the artist rarely thinks about defining objects with complementary outlines. This is unnecessary because of the scale: even non-contrasted objects do not blend into a one. Icon graphics is different. Two variants are possible: either foreground and background colors have to be from different sides of the color chart, or the object should be separated from the background by visible lines and shadows. I will dwell on lines in more detail.
If we think more to the big-size graphics, we can note that in order to highlight contours, we can use all (including the most complex) angles, Bezier curves and borders. Anyway, the line will look ideal due to anti-aliasing. When decreasing the graphic dimensions to the small icon size, situation changes greatly. When each single pixel is equally important and can change the overall appearance of the composition, anti-aliasing is simply unreasonable. It comes that you have to think about the possible line slopes.
The angle you select for the line, specifies the step of this line. This means that every line is made of primary elements, the union of which determines its accuracy and visual appeal.
For instance, a 18-degree slope consists of many small 3-pixel lines connected using a 1-pixel downshift:
This is how almost each line looks like. Primary element followed by joining followed by another basic element. Unfortunately, not each slope makes the line look neet and not messy.
For example, look at 25 and 20-degree slopes:
It can be easily seen which line is more attractive. The 25-degree angle produses a line containing even 2-pixel primary 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, thus, when not combined by other 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 "appropriate" angles have to make as plain primary elements as possible. Thus, the perfect angles are 0 and 90 degrees. In them, 1-pixel basic elements are joined without downshift and form smooth lines. Less perfect are angles which form primary elements of 1, 2, 3 pixel with 1-pixel downshift. Of course, the lines can not be even, but the human sight will process the picture and present to the viewer what you intended to show to him. Also, the following slopes can be considered correct (but at a stretch): slopes with primary elements consisting of unequal lines shifted by more than 1 pixel.
It is the time to move to another problem. In the previous paragraph, I intentionally defined angles with primary elements of 1, 2 and 3 pixels as correct. Such small lines, especially when a great number of them is joined, 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 obviously noticed that the line doesn't have integrity. It is not a continuous line now; it is a combination of several lines, situated near one another. Rarely any designer wants its creation to look that way. So, we come to another conclusion: if you use minimal slopes, which make long primary elements, it has to be reasoned and used with maximum caution.
And, finally, the last thing I wanted to mention about lines. I already wrote that the primary 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 are possible) following ways:
In the first picture the basic element is a 2-pixel line. In the other picture, it is made of three lines: 3-pixel, 2-pixel and 1-pixel. The same angle but the image is different. The complicated basic element made the line untidy.
Such examples can be made for almost any angle, so in your works, try to simplify as much as possible.
It can be said without an exaggeration that the color is the main element of your work; not suiting or poorly matched 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 picture looks poor when converted to monochrome, it means the colors that were used are wrong. This rule is valid not exclusively for icons but for the entire graphic design.
Second, you will probably unable to apply safe RGB. Of course, you can use GIF colors only, but this ties you hand and foot. Gradients, shadows, dithering and many other tricks will not be available to you.
Third, try to increase the areas of "plain" color. The more consistently colored parts without diffusion and jumps your project has, the more clear it looks. Pictograms are too small and the excess usage of complex filters makes the picture look dirty.
Fourth, gradients. This is a great tool which can improve the appearance of any project. Besides visuals, gradients are a perfect way to abolish the "broken line" effect (lines with too long primary elements). But be careful when applying them since too much gradients can ruin the plain color, and be unable to fit into the gif palette.
Fifth, shadows and highlights. All rules for applying shades and flares in icon design are totally the same to the rules of the overall graphic design. The only ine I have to note: draw everything yourself. Don't use filters, make all shadows and highlights in a different layer and then edit its transparency. When applying filters, you almost never know what will it look like. It is bad when you don't control the making of a composition. It is worse if you don't control it when creating miniatures.
And, finally, sixth. Tinting is the main aspect of pictogram creation, which largely affects the visual appearance of the image. If the blue human eye in the icon is sized 1 pixel, increase the color intensiveness. For example, instead of 0, 131, 159 make 71, 195, 242. It doesn't matter that the human eye can't have this color; in the first case it will appear like a gray dot, but in the second example it will really be a blue eye.
Thoroughly control the image, do not allow the visual illusions to ruin your design. It is acceptable if something is not perfect technically, but the whole composition must be flawless.
As an example, I drew the pack of juice located in front of me. The picture has plain color, gradients with broken lines, shades and flares and tints.
If I wrote about something bigger than miniature creation, this part wouldn't fit into a whole book, but the size of images ;limits fonts too.
The size of symbols becomes the leading issue as opposed to their look. Almost in any case, only if not the letters are the main part of the image, the font size must be decreased to the greatest extent possible.
In principle, virtually any design studio has its unique font with little letters. This font can be crafted in several hours. You can browse the web and collect your own collection of very nice fonts. First of all, I would recommend you to download the DS Pixel and Seventen 7Vedi website and the whole series of fonts from the Lakmus Lab website.
If you don't need a new font, little sizes of Arial and Verdana will do. As a last resort, you can create the needed letters 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 cannot 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 perfectly understandable.