The basic German question words form the foundation of conversation. They are Wer? (Who?), Was? (What?), Wo? (Where?), Wann? (When?), Warum? (Why?), and Wie? (How?). A useful phrase is "Wie heißt du?" which literally means "How are you called?" but functions as "What is your name?" You can ask about quantity with Wie viel? (How much?) for uncountable things like prices ("Wie viel kostet das?") and Wie viele? (How many?) for countable items ("Wie viele Kinder hast du?"). These question words can be combined with vocabulary you already know to build an enormous range of simple conversations.
A small set of phrases covers a remarkable amount of self-introduction. To say where you are from, use "Ich komme aus..." followed by a country in the dative case, as in "Ich komme aus den USA" or "Ich komme aus Frankreich." To say where you live, use "Ich wohne in..." with the same preposition plus a place: "Ich wohne in Berlin" or, for countries that take an article, "Ich wohne in der Schweiz" (Switzerland). Your age is expressed with the verb "sein" (to be), not "haben" as English speakers might expect: "Ich bin fünfundzwanzig Jahre alt" (I am 25 years old). To describe what languages you speak, say "Ich spreche Deutsch" (and add "und Englisch" for more than one).
To talk about preferences, German uses "gern" or "gerne" placed after the verb to indicate that you enjoy an activity: "Ich lese gern" (I like to read) or "Ich koche gern" (I like to cook). For liking specific things, the verb "mögen" is used with nouns: "Ich mag Musik" (I like music), "Ich mag Schokolade" (I like chocolate), and "Ich mag Hunde" (I like dogs). To ask about hobbies, you can say "Was ist dein Hobby?" (informal) or "Was ist Ihr Hobby?" (formal), and answer with "Mein Hobby ist Lesen" (My hobby is reading). To describe your family in summary, "Meine Familie ist klein oder groß" gives a starting point, which you can expand with "Ich habe drei Geschwister" (I have three siblings).
One of the most important cultural lessons in German is the distinction between the formal "Sie" and the informal "du." Use "Sie" with strangers, older people, professionals, and in any business or professional setting such as a job interview. Use "du" with friends, family, children, and peers. A useful tip is to wait for the other person to offer "du"; if they suggest it, you might hear "Wir können uns duzen" (We can use du with each other). In a job interview, always use "Sie," for example, "Könnten Sie mir mehr über die Stelle erzählen?" (Could you tell me more about the position?). Switching to "du" uninvited in a professional setting is considered rude. Together, these question words, key phrases, and social rules form a complete toolkit for beginning to communicate in German.