Past tense: Perfekt
The conversational past usually uses haben or sein plus a past participle at the end. Most verbs use haben. Regular participles often use ge- + stem + -t; irregular ones must be learned.
Understand the idea
Perfekt combines a present-tense auxiliary with a past participle. It is very common when talking about past events. German Perfekt does not map exactly onto English present perfect; an English simple-past translation is often natural.
Build it step by step
Conjugate haben for the subject and place the participle at the end of a main clause. Most verbs that take an accusative object and many verbs describing activities use haben. Learn irregular participles individually. In a subordinate clause, the finite auxiliary moves to the end of the verbal group.
See it in a sentence
Ich habe gestern Deutsch gelernt.
Ich habe Kaffee getrunken.
A useful memory aid
Store each new verb with its auxiliary and participle: hat gemacht, hat gelesen. That is more useful than memorising the participle alone.
A common trap
Do not use the infinitive where the participle belongs. Also avoid adding a second personal ending to the participle; the auxiliary already carries agreement.