aus auser bei mit nach seit von zu gegenüber If you see one of these words, the noun following it will be in the accusative prepositional phrase. Use Dem, Der, Dem, Den
Mit dem Freund Bei der Frau Aus dem Hause Seit der Zeit
an auf hinter in neben über unter vor zwischen These prepositions are found in both Accusative and Dative cases depending on the meaning of the sentence.
If the meaning of your sentence conveys movement then the preposition will force the accusative case. (Wohin => Where to) Ich gehe in das Kino. => I am going to the movie. I am going to the movies, I am not there. If the meaning of the sentence conveys no movement then the preposition will force the dative case. (Wo => Where) Ich bin in dem Kino => I am at the movies. I am there, not going anywhere.
Auf dem Tisch (stationary) Auf den Tisch (movement) In dem Café (stationary) In das Café (movement) There are some verbs that will illicit a stationary or movement situation and naturally cant be used with the opposite preposition.
(an)statt trotz während wegen If you see any of these prepositions, the noun following will have the Genetive case. Use Der, Des, Der, Des
Trotz des Mannes Wegen der Situation Anstatt des Geldes
Prepositions are your friend. They will help you identify each component in a sentence. They do not take the place of the sentence components like the Nominative, Accusative and Dative cases. They have their own prepositional cases in the Nom., Acc., and Dative from the sentence structure components. Learn them, remember them and get used to them.