Perfect vs. Preterite

In English we use the preterite about 90% of the time, and we tend to reserve the perfect for situations where a past action has ongoing implications or relevance in the present. For example, consider "have you seen the Godfather movies?" (perfect – if you haven’t, you still could) versus "did you see the circus while it was in town?" (preterite – it’s too late to see it now).

In German, this distinction no longer really exists. There is a single concept of the past (die Vergangenheit) and the Präteritum and Perfekt tenses are interchangeable in expressing it. In practice, Germans use the Perfekt for about 90% of speech; they only use the Präteritum in speech for the auxiliary and modal verbs and a few very common strong or mixed verbs. Overusing the Präteritum in speech will make you sound like a snob or a robot, depending on the context.

Here are the rules you should follow in spoken German:

1. Always use the preterite for sein:

Ich war glücklich.
I was happy.
Es war schönes Wetter auf der Insel.
The weather on the island was nice.
Warst du zu Hause?
Were you home?
Wir waren noch nie in Griechenland.
We've never been to Greece.

2. Always use the preterite for modal verbs:

Ich konnte es nicht sehen.
I couldn't see it.
Das solltest du schon gestern machen.
You were supposed to do that yesterday.
Durfte er nicht mitkommen?
Wasn't he allowed to come along?
Wir wollten aber nicht.
But we didn't want to.

3. Use the perfect tense for everything else:

Ich bin ihm am Sonntag begegnet.
I met him on Sunday.
Was hast du ihm gesagt?
What did you say to him?
Es ist vor langer Zeit gemacht worden.
It was done a long time ago.
Meine Vorfahren haben Deutschland vor 150 Jahren verlassen.
My ancestors left Germany 150 years ago.

You'll hear native speakers using more exceptions than these, of course, but they tend to be verb-by-verb (and often regional) preferences that you have to just pick up by ear.

Written German always uses the Präteritum more than spoken German, but just how much varies according to the context. The Präteritum is most favored in novels, history and other literary/academic writing. For example, here's the opening of a detective novel by the German author Jakob Arjouni. We've highlighted all the conjugated verbs for you:

Endlich schlug ich die Augen auf und ortete die verdammte Fliege. Dick und schwarz saß sie auf der weißen Bettdecke. Ich zielte anständig und stand auf, um mir die Hand zu waschen. Den Spiegel mied ich. Ich ging in die Küche, setzte Wasser auf und suchte Filtertüten. Finally I opened my eyes and located the damned fly. Fat and black, it sat on the white blanket. I aimed well and stood up to wash my hand. I avoided the mirror. I went into the kitchen, set up some water [to boil] and looked for coffee filters.
Arjouni has used every one of those verbs in the Präteritum. Let's review them:
Strong Verbs Präteritum
aufschlagen (to open)
sitzen (to sit)
aufstehen (to stand up)
meiden (to avoid)
gehen (to go)
schlug auf (opened)
saß (sat)
stand auf (stood up)
mied (avoided)
ging (went)
Weak Verbs Präteritum
orten (to locate)
zielen (to aim)
aufsetzen (to set)
suchen (to look for)
ortete (located)
zielte (aimed)
setzte auf (set)
suchte (looked for)

Journalistic content generally leans towards the Präteritum too, although not quite as much. In fact, most news stories begin with either the Präsens or the Perfekt before switching back to the Präteritum. For example:

Angelina Jolie hat mit Partner Brad Pitt in Berlin ihren 38. Geburtstag gefeiert. Dafür mieteten sie eine ganze Restaurant-Etage. Doch das Essen war nicht seine einzige Aufmerksamkeit... Angelina Jolie celebrated her 38th birthday with her partner Brad Pitt in Berlin. They rented an entire floor of a restaurant. But the food wasn't his only gift...

This usage of the Perfekt is one of the few remaining echos in German of that "relevance to the present" distinction. It just sounds a little more up-to-the-minute, more like news to begin a story that way.

Once you get to less formal writing -- personal emails, online posts, text messages -- it's much harder to offer any clear guidelines. You will definitely see a lot more Perfekt in these formats than you would in a novel, often because we tend to affect a looser "spoken" register (in any language) in these kinds of casual writing. But there's also more use of the Präteritum than in speech. The exact mix of the two depends on the person and the context.

All students of German are told to avoid the Präteritum in speech, but few take it seriously enough. The fact is, many native speakers are unaware that certain preterite forms even exist in their language unless they've learned about them in advanced grammar classes. This is especially true of the second-person preterite forms, since books and newspapers are almost never written in the second person. For example, we know a teacher who was giving an English class to young Deutsche Bahn employees, and wanted them to come up with the phrase "what did you (guys) do?" in English. Instead of the normal "Was habt ihr gemacht?" (Perfekt) he asked them to translate "Was machtet ihr?" (Präteritum) so that they wouldn't have "what have you done?" as an option. But "Was machtet ihr?" sounds so odd to modern ears that the students absolutely refused to accept that it was proper German at all!