First, follow what Kaymyth said. Second, just asking for things to improve is the "wrong" way to frame it. You'll want to frame it as you taking the initiative, like "I noticed 'x' the other day and thought 'y' would improve on it. What do you think of 'y'?" In that way, you not only find areas to improve, you show initiative and a willingness to work with others to do stuff in the best way!