How do I tell which buttons are which on an accordion?

In a piano accordion, the bass buttons are organised according to the circle of fifths - so for example, the button above C is G (a fifth higher), and the next one is D (another fifth higher). The button below C is F (a fifth lower). On each horizontal row, you have several different variations of the same chord (except for the first column). For example, on the C row, the second button is a plain C note, the third is a major C chord, the fourth is a minor C chord, the fifth is a dominant 7 C chord, and the sixth is a diminished 7 C chord. It goes this way for all rows.