If you overhear people working through a problem, you shouldn't intermittently lob advice across the room. This can lead to the "too many cooks" problem, but more important, it can be rude and disruptive to half-participate in a conversation. This isn't to say you shouldn't help, offer advice, or join conversations. On the contrary, we encourage all those things. Rather, it just means that when you want to help out or work with others, you should fully engage and not just butt in sporadically.