When do you use the subjunctive in Italian?

The single test

You don't need a list, you need a question. Is the speaker stating that something is, or saying how they see it? *So che Marco è partito states a fact. Penso che Marco sia partito* states an opinion about a fact.

Every rule you've read follows from this. The governing verb changes; the test doesn't.

Where it's compulsory

After verbs of opinion and subjective perception: penso che, credo che, mi sembra che, ho l'impressione che.

After verbs of will, wish and fear: voglio che, spero che, ho paura che, preferisco che. Note that Italian won't take an infinitive across a change of subject: it's voglio che tu venga, never "I want you to come" word for word.

After impersonal expressions: è possibile che, bisogna che, è meglio che, può darsi che.

After certain conjunctions, always: benché, sebbene, affinché, prima che, a meno che, purché.

Where you don't, even though it looks like you should

After so che, è vero che, è certo che, siccome: these assert facts and take the indicative. Learners who have just met the subjunctive put it everywhere — it's the over-correction error, and it's audible.

When the subject is the same, use the infinitive and the question disappears: penso di partire, not penso che io parta.

In everyday speech, many Italians use the indicative after penso che and credo che. It's widespread and passes unnoticed, but it's outside the standard: in an exam, a work email or anything written, use the subjunctive.