general converse, and accurate observation of the living world
One of the highlights of Johnson's novel is that monitoring the lives of people would create a good detail of contemporary experience. It's very different from that of the romance, whose writers Johnson describes as people who "retire to his closet, let loose his invention, and heat his mind with incredibilities". The dichotomy between these two forms of writing is what Johnson saw as the chief difference between the novel and the romance. As a result, in order to write in a completely different way, the novelist must not "retire to his closet".
Johnson, Samuel. The Rambler, 31 March 1750. University of Pennsylvania Department of English, http://www.english.upenn.edu/~mgamer/Etexts/johnson.rambler.html