How do you figure out what substances form a buffer?
A buffer is formed from a weak acid and its salt (conjugate base) OR a weak base and its salt (conjugate acid). For examples:
acetic acid and sodium acetate (its the acetate that is the conjugate base part so it can be sodium acetate, potassium acetate. etc)
ammonia solution and ammonium chloride (or ammonium sulfate, ammonium bromide, ammonium something).