Let's consider purely technical aspects of icon creation
1. Lines, angles
One of the vital parts of the image is the outline of the object, i.e. rough border, which separates the object from the rest of the image. When working with normal-sized graphics, the artist rarely cares about highlighting of objects with additional outlines. This is not needed because of the size: even non-contrasted objects do not blend into a single whole. Icon graphics is different. Two solutions are available: either foreground and background colors must be from different sides of the color wheel, or the foreground must be separated from the background by visible lines and shadows. I would like to discuss lines in more detail.
If we think again to the big-size graphics, we can note that in order to define edges, we can use all (including the most complicated) angles, Bezier curves and edges. In any case, the line will look perfect due to anti-aliasing. When shrinking the graphic scale to the size of an icon, situation changes dramatically. When each single pixel is vitally important and can change the whole look of the composition, anti-aliasing is simply not applicable. It comes that you should think about the possible line angles.
The angle you choose for the line, specifies the step for this line. Because every line consists of primary elements, the union of which determines its accuracy and visual appeal.
For instance, a 18-degree slope contains many tiny 3-pixel lines combined with a 1-pixel downshift:
This is how nearly each line looks like. Basic element with joining and second basic element. However, not every angle creates lines that look look neet and not annoying.
For example, look at 25 and 20-degree slopes:
It can be easily known which line is more attractive. The 25-degree slope makes a line containing equal 2-pixel basic elements. The 20-degree angle has a primary element consisting of three lines: 3-pixel, 3-pixel and 2-pixel. The angle is more complex, therefore, if not supported by other visual effects, it brings a feeling of messiness: the primary elements have contrast which is too strong to escape the human sight.
Here we can see the first rule. The most "appropriate" slopes must make as simple primary elements as they can. Thus, the perfect angles are 0 and 90 degrees. In those, 1-pixel primary elements are joined without downshift and form even lines. Less ideal are slopes which form basic elements of 1, 2, 3 pixel with 1-pixel downshift. Surely, the lines can not be smooth, but the human sight will process the picture and provide to the viewer what you meant to show to him. Also, the following slopes can be considered acceptable (but at a stretch): slopes with basic elements consisting of different lines shifted by more than 1 pixel.
Now we can discuss another issue. In the last paragraph, I intentionally defined angles with basic elements of 1, 2 and 3 pixels as acceptable. Such tiny lines, especially when a large amount of them is combined, appear as a single whole. But what do we see if we change the basic elements to 10 or 20 pixels?
Here is an example:
It can be obviously seen that the line doesn't have solidness. It is not a continuous line now; it is a set of several lines, located near one another. Hardly any designer wants its creation to look inconsistent. So, we come to another conclusion: if you use minimal slopes, which make long primary elements, it must be reasoned and employed with maximum caution.
And, finally, the third aspect I have to mention about lines. I already wrote that the basic element should be as simple as possible.
For instance, a 25-degree slope can be produced in the two (of course more of them are possible) following ways:
In the first case the basic element is a 2-pixel line. In the other case, it consists of three lines: 3-pixel, 2-pixel and 1-pixel. The same slope but the image is different. The complex basic element made the line messy.
Such examples can be produced for almost any slope, so in your projects, try to simplify as much as possible.
It can be said without an overstatement that the color is the leading aspect of your work; not suiting or badly matched colors can ruin even the most creative idea. What can we say about the color in icon graphics?
First, there is a certain rule: if the picture looks bad when converted to monochrome, it means the colors that were selected 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. 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 accessible to you.
Third, try to increase the portion of "plain" color. The more evenly colored areas without diffusion and jumps your composition has, the more neat it appears. Icons are too small and the excess usage of complex effects makes the image look messy.
Fourth, gradients. This is a great instrument which can change the look of any composition. Besides visuals, gradients are a perfect solution to abolish the "broken line" effect (lines with too long primary elements). But be attentive when using them because too much gradients can ruin the flat color, and be unable to fit into the gif palette.
Fifth, shadows and flares. All aspects of using shadows and highlights in icon design are completely identical to the aspects of the overall graphic design. The only thing I would like to note: draw everything by hand. Don't apply filters, make all shades and highlights in a different layer and then edit the opacity. If using effects, you rarely know what will it look like. It is bad when you can't control the making of a composition. It is awful if you don't control it when drawing miniatures.
And, lastly, sixth. Tinting is the key aspect of icon design, which greatly results the esthetic look of the project. When the blue human eye in the picture is sized 1 pixel, increase the color intensiveness. For instance, instead of 0, 131, 159 make 71, 195, 242. It is indifferent that the human eye never has this color; in the first case it will look like a gray dot, and in the second one it will definitely be a green eye.
completely control the image, do not let the visual illusions to ruin your work. It is OK if something is not perfect from the technical point of view, but the whole composition must be flawless.
As an example, I drew the packet of juice standing in front of me. The picture has flat color, gradients with broken lines, shadows and highlights and nuances.
If I wrote about something other than icon design, this chapter wouldn't fit into a whole book, but the resolution of images ;limits fonts too.
The size of symbols is the main aspect as opposed to their look. Nearly in any case, only if not the letters are the main part of the composition, the font size must be decreased to the largest extent possible.
In principle, virtually any graphic studio has its exclusive font with tiny letters. Such a font can be created in a few hours. You can browse the internet and make your own collection of very interesting fonts. Primarily, I would recommend you to download the DS Pixel and Seventen 7Vedi webpage as well as the entire set of fonts from the Lakmus Lab website.
If you don't want a new font, tiny typesizes of Arial and Verdana may do. As a last option, you can create the necessary 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 unrecognizable mixture of pixels.
However, there are no rules without exceptions and the 5-point Arial appears perfectly readable.