You should always remember that any selection in the text disturbs the uniformity of typing and thereby reduces the comfort of reading and, as a result, the perception of information. Therefore, in all unjustified cases, the selection should be abandoned. Any selection, as well as its degree, must be logically justified.
In the first part of the review, the most popular methods of isolation will be presented, as well as possible errors of their application and recommendations on how to avoid it.
1. Selection of uppercase [capital] lettersThis method of selection is widely used as inscriptions on monuments and monuments. The tradition of this distinction dates back to the times of the Roman Empire, with its monumentalism and burden to greatness. This emphasis is appropriate for languages in which short words predominate like Latin. In long words or whole passages, capitalization makes them difficult to read.

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For Cyrillic fonts, unlike Latin ones, this rule is not always suitable, since lowercase letters often repeat the spelling of upper case letters.
2. Set in italicsAllocation in italics is a priority way of font selection, which is the least disturbing of the overall picture of the set. Initially, the italic font was analogous to a handwritten text, but over time it lost more and more of this similarity, becoming just an oblique version of the main headset. This trend contributes to the fact that the italic set loses its attractiveness and strength as a method of isolation.
3. Bold and increase font sizeFat style can rightly be called the most popular selection tool, which does not mean the most successful. Bold style violates the brevity of the set and creates dark spots.
Bold should be used only where you should immediately draw attention to a specific place in the text. A prime example is the flyers.
Also bold is good for highlighting headers. It is worth noting that the bold outline of the main font size is quite enough for selection, so you should not add an increase in size. Only in special cases the bold face can be combined with a size other than the basic size, for example, for titles of different levels. The control authority should always be the logic of the text.
4. Changing the headsetIt is not recommended to mix different headsets, although this method of selection immediately emphasizes attention. Each headset has its own unique style, style and logic of construction. Due to the mixing of the headset, there is a confrontation between two different styles, which in most cases interferes with adequate perception.
If for some reason it is impossible to refuse to mix fonts, at least the use of typefaces of one typographical class should be a prerequisite.
Mixing styles requires a great deal of experience, an understanding of font styles and knowledge of their creation, as well as an unrivaled sense of taste.
5. DischargeDischarging is effective only when a discharged word or group of words is surrounded by a non-polarized text.

In all other cases, the discharge loses its quality of discharge and only introduces randomness and untidiness into the general band of the set. This applies primarily to the discharge of single words, titles, tables of contents, etc.
It is also considered an error to discharge the lines, not because there is a need for selection, but in order to align the length of the lines with respect to each other.
6. Set of capitalAlong with italics, a set of capitals is considered the most successful method of selection. When allocating a capital, one should always remember about the need for discharge and all the limitations associated with it.

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7. Highlighting with lines and borders.The simplest selection of lines is the underscore. Almost always this selection fails, harming the balance of the word.

This can be avoided by using color underlining, or, even better, try to complement the lines or, at least, designate the simplest geometric image.

The limit of lines and borders is white text on a black background.

Literature:
Paul Renner, Die Kunst der Typographie