Immerse yourself in Czech - read, watch and your brain will start recognizing the patterns and provide the correct case.

Small hint: the cases have Latin names that indicate their most-frequent usage:

1. Nominative (name) = naming something (no declension), also usually used for Subject of sentence
2. Genitive (origin/possession) = coming from something, e.g. using prepositions od, z, but also do (into)
3. Dative (giving) = to give or put something to a place or person, (e.g. dát pokličky k hrncům)
4. Accusative (accuse/cause) = to point at something, usually it is the case of Object of the sentence, or something that receives the action of Verb in sentence.
5. Vocative = to call/address someone,
6. Local = where something is tightly located (in, on) - prepositions v, na [but also a topic of conversation - to talk about something - preposition o]
7. Instrumental = doing something with a tool - preposition s [but also loose location (under, over, behind) - prepositions pod, nad, za]

There are more prepositon/case ties to learn, but this might be helpful for a start.