I would say before you even start doing slow rolls, master two other maneuvers first: 3 rolls, and 3 loops.

The 3 rolls should start straight and level, traveling with the wind and should be in as straight a line as possible as if the plane had a wire running through the nose to the tail. (Note: this maneuver is the precursor to learning slow rolls)

The three loops should start straight and level, into the wind, and should be round and one on top of the next, as if, if you were blowing a smoke trail, you would only see ONE circle. (This maneuver is the precursor to other maneuvers such as Cuban 8's)