Let's consider purely technical aspects of icon creation
1. Lines, slopes
One of the most important parts of the composition is the framework of the object, i.e. rough line, which limits the object from the rest of the image. When designing large-scale images, the artist occasionally thinks about defining objects with complementary outlines. This is unnecessary because of the size: even non-contrasted objects do not blend into a single whole. Pixel graphics is different. Two solutions are available: either foreground and background colors have to be from opposite sides of the color wheel, or the foreground should 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 contours, we can use all (even the most complicated) angles, Bezier splines and borders. Anyway, the line will appear ideal thanks to anti-aliasing. When decreasing the graphic scale to the size of an icon, situation changes dramatically. When each particular pixel is equally valuable and can change the whole appearance of the icon, anti-aliasing is simply unreasonable. It comes that you should consider the possible line angles.
The angle you select for the line, specifies the step for this line. Because every line consists of basic elements, the union of which determines its neatness and visual appeal.
For instance, a 18-degree slope contains many small 3-pixel lines combined with a 1-pixel downshift:
This is how almost every line looks like. Basic element followed by joining followed by another primary element. However, not every angle makes the line look neet and not annoying.
For example, here are 25 and 20-degree angles:
It can be easily seen which line is more attractive. The 25-degree slope makes a line consisting of equal 2-pixel primary elements. The 20-degree slope has a primary element containing of three parts: 3-pixel, 3-pixel and 2-pixel. The angle is more complicated, thus, when not supported by other visual effects, it brings a feeling of messiness: the basic elements have contrast which is too obvious to escape the human sight.
Here we can come to the first rule. The most "appropriate" slopes have to make as simple basic elements as they can. Thus, the perfect angles are 0 and 90 degrees. In those, 1-pixel primary elements are combined without any shift and form smooth lines. Less ideal are slopes which form primary elements of 1, 2, 3 pixel with 1-pixel downshift. Of course, the lines will not be even, but the human sight will process the image and present to the viewer 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.
It is the time to touch another problem. In the previous paragraph, I intentionally defined angles with primary elements of 1, 2 and 3 pixels as acceptable. Such tiny lines, especially when a large amount of them is combined, appear as solid. But what do we see if we change the primary elements to 10 or 20 pixels?
Here is an example:
It can be obviously noticed that the line loses its solidness. It is not a continuous line anymore; it is a combination of several lines, situated near one another. Hardly any designer wants its creation to look that way. Thus, we come to the second rule: if you use minimal angles, which produse long basic elements, it has to be reasoned and employed with maximum attention.
And, finally, the third aspect I wanted to mention about lines. I already wrote that the basic element should be as simple as it can.
For example, a 25-degree angle can be drawn 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 consists of three lines: 3-pixel, 2-pixel and 1-pixel. The same slope but the look is different. The complicated basic element produced the line messy.
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 main aspect of your work; not suiting or poorly balanced colors can kill even the most creative idea. What can we say about the color in icon graphics?
First, there is a certain rule: if the image looks poor when converted to monochrome, it means the colors that were selected are wrong. This rule is valid not exclusively for icons but for the entire graphic design.
Second, you will be unable to use common RGB. Of course, you can select internet colors only, but this limits you greatly. Gradients, shadows, dithering and many other effects will not be available to you.
Third, try to enlarge the portion of "flat" color. The more consistently colored parts without blurring and jumps your picture has, the more neat it appears. Pictograms are too tiny and the over usage of special filters makes the picture look messy.
Fourth, gradients. This is a great instrument which can change the appearance of any project. Other than visuals, gradients are a perfect way to abolish the "broken line" look (lines with too long primary elements). But be careful when using them since too many gradients can ruin the flat color, and be unable to fit into the gif palette.
Fifth, shadows and flares. All aspects of applying shadows and flares in icon design are completely identical to the aspects of the general graphic design. The only thing I have to mention: create everything by hand. Don't apply effects, make all shades and flares in a different layer and after that edit the opacity. If using filters, you almost never can predict what will it look like. It is unfavorable when you can't control the making of a composition. It is awful if you can't control it if drawing icons.
And, finally, sixth. Nuancing is the main aspect of icon creation, which greatly results the visual appearance 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 doesn't matter that the human eye never has such color; in the first example it will appear like a gray dot, and in the second one it will really be a green eye.
completely control the image, do not let the visual illusions to spoil your design. It is acceptable if something is not perfect from the technical point of view, but the whole picture must be perfect.
As an example, I pictured the packet of juice standing before me. The image has plain color, gradients with broken lines, shadows and highlights and tints.
If I talked about something other than miniature creation, this part wouldn't fit into an entire book, but the size of pictures restricts fonts too.
The size of letters is the main issue as opposed to their beauty. Nearly in any case, unless the letters are the primary part of the composition, the text size must be reduced to the greatest extent possible.
In principle, virtually any graphic studio has its unique font with little characters. This font can be made in several hours. You can browse the web and make your own collection of very nice fonts. First of all, I advice you to download the DS Pixel and Seventen 7Vedi webpage as well as the complete set 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 option, you can draw the needed letters yourself.
There are quite a few 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 text into an unrecognizable set of pixels.
However, there are no rules without exceptions and the 5-point Arial appears rather readable.