Let's consider strictly technical details of icon creation
1. Lines, angles
One of the vital parts of the composition is the framework of the object, i.e. solid line, which separates the object from the rest of the image. When working with normal-sized graphics, the artist rarely thinks about highlighting of objects with complementary lines. This is not needed because of the scale: even low contrast objects do not blend into a one. Pixel graphics is other story. Two solutions are available: either object and background colors have to be from different sides of the color chart, or the object should be divided from the background by visible lines and shadows. I will discuss lines deeper.
If we return more to the large scale images, we see that in order to define edges, we can use any (including the most complex) angles, Bezier curves and borders. In any case, the line will appear ideal thanks to anti-aliasing. When decreasing the graphic scale to the small icon size, situation changes greatly. When each single pixel is equally valuable and can change the whole appearance of the icon, anti-aliasing is simply not applicable. It means that you should consider the possible line angles.
The slope you select for the line, specifies the step of this line. Because every line consists of primary elements, the combination of which defines its neatness and esthetics.
For instance, a 18-degree angle consists of many tiny 3-pixel lines combined with a 1-pixel downshift:
This is how nearly each line looks like. Primary element followed by joining followed by second primary element. However, not every angle creates lines that look look neet and not messy.
For example, here are 25 and 20-degree slopes:
It can be easily known which line is more attractive. The 25-degree angle produses a line consisting of equal 2-pixel primary elements. The 20-degree slope has a primary element consisting of three parts: 3-pixel, 3-pixel and 2-pixel. The slope is more complex, thus, when not supported by additional visual effects, it creates a feeling of messiness: the basic elements have contrast which is too obvious to hide from the human eye.
Here we can come to the first conclusion. The most "correct" slopes must make as plain primary elements as possible. Thus, the ideal slopes are 0 and 90 degrees. In them, 1-pixel basic elements are joined without any shift and form smooth lines. Less perfect are slopes which form primary elements of 1, 2, 3 pixel with 1-pixel downshift. Surely, the lines can not be even, but the human brain will process the image and provide to the viewer what you meant to show to him. Also, the following angles can be considered acceptable (but at a stretch): angles with primary elements made of different lines shifted by more than 1 pixel.
Now we can touch another issue. In the last paragraph, I purposely defined slopes 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 a single whole. But what happens if we change the basic 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 continuous line now; it is a set of several lines, located near each other. Hardly any artist wants its creation to look inconsistent. Thus, we have the second rule: if you use small slopes, which produse long primary elements, it has to be justified and employed with great attention.
And, finally, the third thing I have to mention about lines. I already wrote that the basic element has to be as simple as it can.
For instance, a 25-degree slope can be drawn in the two (sure more of them exists) following ways:
In the first picture the basic element is a 2-pixel line. In the second case, it consists of three elements: 3-pixel, 2-pixel and 1-pixel. The same angle but the image is different. The complex primary element produced the line untidy.
This examples can be made for about any slope, so in your works, try to simplify as much as possible.
It can be said without an exaggeration that the color is the main aspect of your work; improper 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 image looks poor when converted to grayscale, it means the colors that were selected are wrong. This rule is true not only for icons but for the whole graphic design.
Second, you will be unable to use 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 accessible to you.
Third, try to enlarge the portion of "flat" color. The more evenly colored parts without blurring and jumps your project has, the more neat it looks. Icons are too small and the over usage of complex filters makes the image look dirty.
Fourth, gradients. This is a wonderful instrument which can change the appearance of any project. Besides visuals, gradients are a perfect solution to abolish the "broken line" effect (lines with too long basic elements). But be attentive when applying them because too many gradients can ruin the plain color, and be not suitable for the gif palette.
Fifth, shadows and highlights. All aspects of using shades and flares in icon design are completely identical to the aspects of the general graphic design. The only ine I have to mention: draw everything yourself. Don't apply effects, make all shades and highlights in a separate layer and then edit its transparency. If using filters, you rarely know what the result will be. It is bad when you don't control the process of creating of a composition. It is awful if you can't control it when drawing icons.
And, finally, sixth. Tinting is the key aspect of icon creation, which largely affects the visual look of the project. When the blue human eye in the icon has the size of 1 pixel, increase the color intensiveness. For example, instead of 0, 131, 159 choose 71, 195, 242. It is indifferent that the human eye can't have this color; in the first case it will look like a gray dot, and in the second one it will really be a blue eye.
completely control the picture, do not allow the visual illusions to spoil your work. It is OK if something is not perfect technically, but the entire composition must be flawless.
As an example, I pictured the packet of juice standing before me. The picture has plain color, gradients with broken lines, shadows and highlights and tints.
If I talked about something bigger than pictogram design, this part wouldn't fit into an entire book, but the size of images restricts fonts too.
The size of letters is the leading issue as opposed to their beauty. Nearly in any case, only if not the letters are the primary part of the image, the font size must be reduced to the largest extent possible.
In general, virtually any graphic studio has its exclusive font with small letters. Such a font can be made in a couple of hours. You can browse the internet and make your own library of very interesting fonts. Primarily, 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 need a new font, tiny typesizes of Arial and Verdana may work. As a last resort, you can draw the needed characters by hand.
There are not many rules there. First, characters 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 unrecognizable set of pixels.
Though, there are no rules without exceptions and the 5-point Arial looks rather understandable.