Verbs:Das Perfekt - Einführung
In order to describe actions that happened in the past, you can use the so-called Perfekt tense, which is used in conversations or informal writing.
The Perfekt tense is sometimes also called Present Perfect, but this name is misleading for American learners, since the English present perfect (Wolfgang has not eaten Little Red Riding Hood) has a slightly different meaning from the basic past tense (Wolfgang did not eat Little Red Riding Hood). In the first case, he still has hope ... in the second one, a completed situation (opportunity lost) in the past is simply described. In German the Perfekt, for the most part, has the same meaning as the Simple Past:
The Perfekt and the Simple Past forms are used in different types of interactions (informal/casual vs. formal). Sometimes the distinction is made between oral versus written use, but that is not quite accurate, because some types of writing are less formal (e.g., E-mail, a weblog) than some types of speaking (e.g., a formal lecture, accepting your Nobel prize, etc.). It is better to remember that the Perfekt is used for informal interaction, and Simple Past is more formal.
You can use any verb with the present perfect, but in High German (a type of "standard" German) some verbs are preferred in the simple past (and you might sound overly casual if you use these verbs with the Perfekt.
haben, sein, wissen + the modal verbs (dürfen, können, müssen, mögen, möchten, sollen, wollen)
Certain dialects (e.g., Bavarian or Swiss or Austrian dialects), in contrast, prefer the Perfekt over the simple past, and younger speakers tend to emphasize the Perfekt as well.
The Perfekt tense is formed by using the participle form of a verb, plus either haben or sein as a helping verb (also called auxiliary verbs).
Auxiliary (helping) verbs
Haben is used as a helping verb when the main verb has or can have a direct object.
Little Red Riding Hood and her grandmother are the direct objects of the verb "to save" in the first sentence, and them is the direct object of the verb "to cut out" in the second sentence.
Sein is used as a helping verb when the main verb expresses a change of state in one's physical or mental state, or in one's physical location (and in a few exceptions even when the verb doesn't take an object, and it doesn't describe change: bleiben, sein).
A few useful verbs with haben/sein