I found this.
Sounds simple to me...
1. The nominative answers the questions "who?" or "what?". It is an initial form. All dictionaries give nouns in the nominative.
Студент читает The student is reading.
2. The genitive is used to show that something (somebody) belongs or refers to something (somebody). It can be translated by "of" in English.
берег реки the bank of the river
3. The dative designates that something is given or addressed to the person (object).
Я иду к врачу I go to the doctor
Я даю это другу I give it to the friend
4. The accusative designates the object of an action.
Я читаю газету I read the newspaper
Я встретил друга I met the friend
5. The instrumental is used to denote an instrument that helps to make something.
Я пишу карандашом I write with a pencil
6. The prepositional is used to designate a place, or a person (object) that is an object of speech and thought. This case is always used with a preposition.
Она мечтает о лете She dreams about the summer
Цветы стоят на столе The flowers are on the table