Politeness in Japanese is conveyed on two axes: one of politeness (or gentility, if it makes the double use of the word less confusing) and one of status.
Gentility refers to one’s disposition, to one’s character, to the energy one wishes to convey. This is very simply handled in Japanese.
Status refers to acknowledgments of how the people involved into a discussion are related. There are people who are higher than you in status; and there are people lower than you in status. Japanese has no language of condescension, so to speak to someone on an equal level is to talk to them “plainly.”
The dimension of status, then, concerns itself with a view towards people of higher status: how one refers to them and their actions (honorific language) and how one refers to one’s own (humble language.)
Here’s something interesting: the language one uses for a person is determined by the person one is talking to.
What does this mean?
If you are talking to your boss, you refer to your boss with honorific language, and to yourself with humble language.
But if you are talking to a customer, you refer to them with honorific language, to yourself with humble language, and to your boss in humble language – because you are representing the company or business and the company as a whole is subservient to its customers.
Likewise, if you talk about your family, because they are an extension of you, you speak about them with humble language rather than with honorific language. (You really don’t “show off” your family in Japanese culture)
Polite Verbs (Teineigo)
To make a verb polite, you take the verbal stem, add the appropriate mood suffix, and add an -ιmas suffix to it; and then a subsequent temporal/polar suffix to it.
/ι/ stands for a weak vowel that appears in the surface form of a word as an /i/ whenever the lexical stem of the verb does not end in /ε/, which is a vowel that occasionally appears in the surface form as /e/ and sometimes not at all. I talk all about it in my verb runthrough.
The temporal/polar suffixes are these:
Affirmative Present/Future: -u
Affirmative Past: -ita
Negative Present/Future: -en
Negative Past: en deshita (periphrastic)
For verbs that use ω as a temporal/polar suffix (ω being what ends up as i/katta/kunai/nakatta):
You can add the polite form of the copula da, desu, to the end to take more polite, albeit semi-illogical. In this case, the verb desu is not acting as a verb but as a politeness suffix.
Here’s the catch: Japanese admits this kind of politeness as standard only when it is the verb of a verb phrase that is not embedded into another verb phrase. This means that indirect quotes are not conjugated for politeness, and neither are attributive phrases.
Humble Verbs (Kenjougo) and Honorific Verbs (Sonkeigo)
Humble Verbs and Honorific Verb are a bit more tricky, because there exist a few verbs that imply humility and are used in humble language.
Let’s look at a quick table where there they use Teineigo and Kenjougo and Sonkeigo together.
(Courtesy of https://en.wikibooks.org/wiki/Japanese/Grammar/Honorifics)
(And if you’re a bit more confident with your Kanji reading, you can visit more thorough listings here and here)
Note: The three very important verbs this list misses are “morau” and “kureru.” “Morau”’s Kenjougo equivalent is “itadaku;” the Sonkeigo equivalent to “kureru” is “kudasaru;” the Kenjougo equivalent to “ageru” is “Sashiageru.”
Other than these exceptions, which are admittedly very common verbs, the verb construction is to take the verb’s verbal stem, add the prefix o- and the verb “suru” in Kenjougo and “naru” in Sonkeigo.
Sonkeigo: o + verbal stem + naru
Kenjougo: o+ verbal stem + suru
If there exist a special verb with the humility or honor implied (so if it’s part of the list), then one does not use this construction.
Kenjougo and Sonkeigo work along with Teineigo as seen in the table, but this is only when applicable, not all the time. It tends to be that if you are going to work along the status axis, you are going to be making your verbs polite. The only place where this is not the case is in anime and perhaps some dramas, where you hear the governing verbs of IPs in their plain form.
Address suffixes are also considered part of Keigo.
To speak on those briefly, for this is probably the most common form of Keigo.
The standard address suffix for people is -san.
The address for people of authority who have some form of didactic/guiding role is -sensei.
The address for someone who is of a higher rank than you but not -sensei, used mainly in schools by lowerclassmen to upperclassmen is -senpai.
The -sama address is used for someone of an unbelievably high rank, like high religious figures and royalty.
The address suffix -kun is used towards young males.
The address suffix -chan is an address suffix used for children and animals; and it is also an intimate address suffix for young girls. Note that -kun and -chan are not equivalent. A young girl can call a young boy -kun without knowing him well, but the boy cannot call the girl -chan.
The intimate address suffix -bou exists for males, but does not carry into adolescence, and thus is used for small boys.