Well, in German it's words at the beginning of a sentence and names, like in English, plus all nouns. Occasionally you'll have adjectives functioning as nouns and those are only sometimes capitalized, but that's advanced. Don't worry about that yet. Adjectives functioning as adjectives are never capitalized (e.g. "Berlin ist eine deutsche Stadt"), except for city-adjectives (e.g. "Currywurst ist ein Berliner Gericht").