Let's discuss strictly technical details of icon making
1. Lines, slopes
One of the most important elements of the image is the outline of the object, i.e. rough line, which limits the object from the background. When designing normal-sized graphics, the designer occasionally thinks about highlighting of objects with complementary lines. This is not needed because of the size: even non-contrasted objects do not blend into a one. Icon graphics is other story. Two solutions are available: either foreground and background colors must be from different 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 big-size images, we see that in order to highlight contours, we can use all (including the most complicated) angles, Bezier splines and edges. In any case, the line will look perfect due to anti-aliasing. When shrinking the image dimensions to the size of an icon, situation changes dramatically. When every particular pixel is vitally valuable and can ruin the overall look of the composition, anti-aliasing is just unreasonable. It comes that you have to consider the possible line angles.
The slope you select for the line, specifies the step of this line. Because each line is made of basic elements, the union of which defines its neatness and visual appeal.
For instance, a 18-degree slope contains many tiny 3-pixel lines connected using a 1-pixel downshift:
This is how nearly every line looks like. Primary element followed by joining followed by second primary element. However, not every angle makes the line look attractive and not annoying.
For example, here are 25 and 20-degree slopes:
It can be easily known which line is more appealing. The 25-degree angle produses a line consisting of equal 2-pixel primary elements. The 20-degree angle has a primary element consisting of three lines: 3-pixel, 3-pixel and 2-pixel. The slope is more complicated, thus, if not combined by other visual effects, it creates a feeling of untidiness: the basic elements have contrast which is too strong to escape the human eye.
Here we can see the first conclusion. The most "appropriate" angles have to make as simple primary elements as they can. Thus, the perfect angles are 0 and 90 degrees. In those, 1-pixel basic elements are combined without downshift and produce smooth lines. Less perfect are slopes which form basic elements of 1, 2, 3 pixel with 1-pixel downshift. Surely, the lines will not be smooth, but the human brain will process the image and present to the user what you meant to show to him. Also, the following slopes 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 move to another problem. In the previous paragraph, I purposely defined slopes with basic elements of 1, 2 and 3 pixels as acceptable. Such tiny lines, especially when a great number of them is combined, look like solid. But what do we see if we increase the primary elements to 10 or 20 pixels?
Here is an example:
It can be clearly noticed that the line loses its solidness. It is not a single line anymore; it is a set of several lines, situated near each other. Rarely any artist wants its composition to look inconsistent. So, we have another rule: if you use minimal angles, which make long basic elements, it has to 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 it can.
For instance, a 25-degree angle can be drawn in the two (sure more of them are possible) following ways:
In the first case the primary element is a 2-pixel line. In the second case, it is made of three lines: 3-pixel, 2-pixel and 1-pixel. The same angle but the image is different. The complicated primary element made the line messy.
Such examples can be made for almost any angle, so in your projects, try to simplify everything.
It can be stated without an overstatement that the color is the leading aspect of your work; not suiting or badly balanced colors can ruin even the best idea. What can we say about the color in miniature graphics?
First, there is a clear rule: if the picture looks poor when converted to grayscale, it means the colors that were used are wrong. This rule is true not only for icons but for the whole graphic design.
Second, you will probably unable to use common RGB. Sure, you can use GIF colors only, but this limits you greatly. Gradients, shadows, blending and many other effects will not be accessible to you.
Third, try to enlarge the portion of "flat" color. The more consistently colored areas without diffusion and jumps your picture has, the more clear it appears. Pictograms are too small and the over usage of complex effects makes the picture look dirty.
Fourth, gradients. This is a great instrument which can change the appearance of any composition. Other than visuals, gradients are a perfect way to get rid of the "broken line" look (lines with too long primary elements). But be careful when applying them since too many gradients can kill the plain color, and be unable to fit into the gif palette.
Fifth, shadows and highlights. All aspects of using shadows and highlights in icon creation are completely the same to the aspects of the overall graphic design. The only ine I have to note: create everything by hand. Don't apply effects, make all shadows and flares in a separate layer and then edit the opacity. If using filters, you rarely can predict what the result will be. It is unfavorable when you don't control the making of a composition. It is worse if you can't control it when drawing miniatures.
And, lastly, sixth. Nuancing is the key detail of icon design, which largely results the visual appearance of the image. If the blue human eye in the image has the size of 1 pixel, increase the color intensiveness. For instance, instead of 0, 131, 159 make 71, 195, 242. It is indifferent that the human eye can't have such color; in the first example it will appear like a gray dot, but in the second example it will definitely be a blue eye.
completely control the picture, do not let the optical tricks to ruin your work. It is OK if objects is not consistent technically, but the entire composition must be perfect.
As an example, I drew the packet 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 pictogram creation, this chapter 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 fineness. Nearly in any case, unless the letters are the primary part of the project, the font size must be reduced to the greatest extent possible.
In principle, virtually any design studio has its unique font with little letters. Such a font can be crafted in several hours. You can browse the web and make your own library of very nice fonts. Primarily, I advice you to download the DS Pixel and Seventen 7Vedi webpage and the whole set of fonts from the Lakmus Lab website.
If you don't want a new font, tiny typesizes of Arial and Verdana will do. As a last option, you can create the necessary characters yourself.
There are not many rules there. First, characters cannot be less than 5 pixels high or less than 3 pixels wide.
Second, letters should not use anti-aliasing. It transforms the font into an incomprehensible set of pixels.
Though, there are no rules without exceptions and the 5-point Arial looks rather readable.