Forming the Tense With Weak Verbs
It's a lot easier to form the perfekt tense in German than it looks. Just like English, German has two main kinds of action verbs. In English, we call them "regular" and "irregular" -- the regular verbs follow a predictable pattern, while the "irregular" ones don't. In German, they're called schwach (weak) and stark (strong).
Look at the following examples. "Break" is irregular (English) and strong (German). The participle form of "break" in English is "broken" -- in German, the participle form of brechen is gebrochen. "Collect" is regular (English) and weak (German) The participle form of "collected" in English is "collected" -- in German, the participle form of sammeln is gesammelt.
If you're dealing with German weak verbs, the pattern is always the same. Take the verb spielen (to play). To form the perfekt, just stick a "ge-" prefix on the beginning, and replace the "-en" with a "t." Example:
English: I have played soccer for three years.
German: Ich habe Fuβball drei Jahren gespielt.
Note the placement -- your helping verb goes in the normal verb position (right after the subject), and the participle, which shows the action, goes all the way to the end. This is one reason why, if you talk to a German person in English, he may say something odd like "I am to the store going" -- Germans are used to putting the action verb at the end when a helping verb appears in the sentence.
One exception -- if your weak verb ends in "-ieren," there is no prefix, but you still put in the "t." Look at this example using telefonieren (to telephone).
English: I called Brian last Thursday.
German: Ich habe Brian letzten Donnerstag telefoniert.
What if there's a separable prefix? Look at this example using aufmachen (to open).
English: I've opened the door for that stupid dog five times!
German: Ich habe die Tür fünfmal für jenen dummen Hund aufgemacht!
Notice that the "ge-" prefix goes between the separable prefix and the main verb. If there is an inseparable prefix (miss-, be-, ver-, and so on), you don't add a prefix -- just the "t." Example:
English: We've been trying all night.
German: Wir haben die ganze Nacht versucht.