How do you form the "Perfekt"?

To form the "Perfekt" is formed: sein/haben + Partizip II (past participle), which is why you need to know how to conjugate the verbs "sein" and "haben":ich bin, du bist, er/sie/es ist, wir sind, ihr seid, sie sind; ich habe, du hast, er/sie/es hat, wir haben, ihr habt, sie habenNext you need to know if the verb is a strong or weak one (which is something you have to memorise).For strong verbs (i.e. verbs which change their stems) the past participle is: ge + verb stem + en (e.g. laufen --> gelaufen)For weak verbs (i.e. verbs which do not change their stems) the participle is: ge + verb stem + (e)t (e.g. kochen --> gekocht)For verbs which have a prefix which is separable from the verb, the past participle is formed as before and the prefix is hung in front of the participle (i.e. it comes before the "ge"), e.g. vorlaufen --> vorgelaufenIf the prefix is inseparable from the verb however, "ge" is omitted. (e.g. verlaufen --> vergelaufen=verlaufen) The verb stem might change in this case though, e.g. verbrennen --> verbranntAnd as always, there are a lot of exceptions, so practice is needed.