The imperative mood is the way people talk when they want to give instructions, orders or directives to others. In English, the spelling and pronunciation of verbs in the imperative are indistinguishable from ordinary present tense. You would say "you read" whether you are describing someone reading or ordering him to read. German works differently, with imperatives taking a different spelling and pronunciation.
When to Use the Imperative
Imperatives are always directed at other people, as you can't order yourself to read a book or march up a hill. Consequently, German imperatives have conjugations only in the second-person singular and plural and in the first-person plural. Imperatives don't have past tense or future tense versions, because commands are always given in the present. Spellings are similar but distinct from the present indicative tense. English speakers typically eschew the imperative mood except when talking to children or subordinates for fear of seeming rude. In Germany, however, imperatives are not considered rude and are used frequently in everyday conversation.
Second-Person Singular Conjugations
To conjugate most verbs in the imperative singular, simply chop off the ending of the normal second-person present tense version of the word. For example, the word "studierst" means "you study." To change this from an observation to a command, drop the "-st" ending and say "studier!" Second-person singular verbs ending in "s," "z" or "x" follow a similar pattern. "Liest," meaning "you read," becomes an imperative by dropping the t and saying "Lies!" Infinitives ending in "m" and "n" are a bit tricker. To change "änderst," or "you change," into a command, chop off the "st" ending and add an "e" to create "ändere."
Unlike in English, German verbs change conjugations in the second person when the speaker is addressing more than one person. Happily, second-person plural imperatives are easy to conjugate because they are identical to the the standard second-person plural present tense conjugation. Thus, you would say "studiert" whether you wish to order a group of people to study or just observe that they are currently studying. Similarly, "arbeitet" means "you (plural) work" and can be either imperative or present indicative.
Though you can't give yourself an imperative in German, you can use the mood when speaking collectively for a group of people as in "let's sing" or "let's walk." This is one very easy: Just add the word "wir," after the infinitive of the verb. To say "let's read," for example, you'd say "lesen wir." "Let's drink," a useful phrase at the local pub," translates to "trinken wir."
Three common auxiliary verbs, "sein," haben" and "werden," meaning "to be," "to have" and "to become," don't follow any particular pattern. "Sein" becomes "sei" in the second-person singular and "seid" in the plural. "Haben" turns into "hab" and "habt," so to translate "Have patience!" to an anxious child, you'd say "Hab geduld!" "Werden" changes to "werde" and "werdet."