Let's consider strictly technical aspects of icon making
1. Lines, slopes
One of the most important parts of the image is the framework of the object, i.e. solid border, which limits the object from the rest of the image. When working with normal-sized graphics, the artist occasionally cares about defining objects with complementary outlines. This is unnecessary because of the size: even non-contrasted objects do not mix into a one. Pixel graphics is other story. Two variants are possible: either foreground and background colors have to be from opposite sides of the color chart, or the foreground should be separated from the background by contrast lines and shadows. I will dwell on lines in more detail.
If we think again to the large scale graphics, we can note that in order to highlight contours, we can use all (including the most complicated) angles, Bezier curves and edges. Anyway, the line will appear ideal thanks to anti-aliasing. When shrinking the graphic scale to the small icon size, situation changes greatly. When each particular pixel is vitally valuable and can ruin the overall appearance of the icon, anti-aliasing is just not applicable. It means that you should think about the possible line slopes.
The slope you select for the line, specifies the step for this line. This means that each line is made of basic elements, the union of which defines its accuracy and esthetics.
For instance, a 18-degree slope contains many tiny 3-pixel lines connected using a 1-pixel downshift:
This is how nearly each line looks like. Basic element followed by joining followed by another primary element. Unfortunately, not every angle creates lines that look look attractive and not messy.
For example, here are 25 and 20-degree angles:
It can be easily known which line is more attractive. The 25-degree slope makes a line consisting of equal 2-pixel basic elements. The 20-degree angle has a basic element containing of three lines: 3-pixel, 3-pixel and 2-pixel. The slope is more complicated, therefore, when not supported by additional visual effects, it brings a feeling of messiness: the primary elements have contrast which is too strong to hide from the human sight.
Here we can come to the first rule. The most "correct" angles must make as plain 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 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 sight will process the image and provide to the viewer what you intended to show to him. Also, the following angles can be considered correct (but at a stretch): slopes with basic elements consisting of unequal lines shifted by more than 1 pixel.
Now we can touch another issue. In the last paragraph, I intentionally defined slopes with primary elements of 1, 2 and 3 pixels as correct. Such small lines, especially when a great number of them is joined, look like solid. But what happens 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 single line now; it is a set of different lines, located near one another. Hardly any designer wants its composition to look inconsistent. Thus, we come to another rule: if you use small slopes, which make long basic elements, it must be reasoned and employed with maximum caution.
And, finally, the last aspect I wanted to mention about lines. I already wrote that the basic element should be as plain as possible.
For example, a 25-degree angle can be produced in the two (sure more of them are possible) following ways:
In the first picture the basic element is a 2-pixel line. In the second picture, it is made of three lines: 3-pixel, 2-pixel and 1-pixel. The same angle but the look is different. The complex basic element made the line messy.
Such examples can be produced for almost any angle, so in your works, make sure to simplify as much as possible.
It can be said without an exaggeration that the color is the main element of your work; improper or badly matched colors can kill even the most creative 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 grayscale, then the colors that were used are incorrect. This rule is true not only for icons but for the entire graphic design.
Second, you will be unable to apply safe RGB. Of course, you can use internet colors only, but this limits you greatly. Gradients, shadows, blending and many other effects will not be available to you.
Third, try to enlarge the portion of "plain" color. The more evenly colored areas without diffusion and jumps your project has, the more neat it appears. Pictograms are too tiny and the over usage of special effects makes the picture look messy.
Fourth, gradients. This is a wonderful instrument which can change the look of any picture. Other than visuals, gradients are an ideal solution to get rid of the "broken line" effect (lines with too long primary elements). But be attentive when applying them because too many gradients can ruin the flat color, and be unable to fit into the gif palette.
Fifth, shadows and flares. All rules for using shadows and highlights in icon creation are completely the same to the aspects of the overall graphic design. The only thing I would like to note: create everything by hand. Don't apply filters, make all shadows and flares in a different layer and then edit the opacity. If using filters, you rarely know what will it look like. It is unfavorable when you can't control the process of creating of a composition. It is awful if you don't control it if creating icons.
And, lastly, sixth. Tinting is the main detail of icon design, which greatly results the visual appearance of the project. When the green human eye in the picture has the size of 1 pixel, increase the color saturation. For example, instead of 0, 131, 159 make 71, 195, 242. It is indifferent that the human eye can't have this color; in the first example it will look like a gray dot, and in the second example it will really be a blue eye.
completely control the image, do not let the visual tricks to ruin your work. It is acceptable if objects is not consistent technically, but the entire composition must be perfect.
As an example, I drew the packet of juice standing in front of me. The picture has plain color, gradients with broken lines, shades and highlights and tints.
If I wrote about something bigger than miniature design, this chapter wouldn't fit into a whole book, but the resolution of images restricts fonts too.
The size of symbols becomes the leading issue as opposed to their beauty. Nearly in all cases, only if not the letters are the main part of the image, the font size must be reduced to the greatest extent possible.
In principle, almost any design studio has its unique font with tiny letters. This font can be created in several hours. You can browse the web and make your own collection of very nice fonts. First of all, I would recommend you to get the DS Pixel and Seventen 7Vedi webpage and the whole series of fonts from the Lakmus Lab website.
If you don't need a new font, little typesizes of Arial and Verdana may work. As a last resort, you can draw the necessary letters by hand.
There are quite a few rules there. First, letters cannot be less than 5 pixels high or less than 3 pixels wide.
Second, letters should not use anti-aliasing. It turns the text into an incomprehensible mixture of pixels.
Though, there are no rules without exceptions and the 5-point Arial looks perfectly understandable.