While perspective is a handy device to construct imagined spaces, it is not useful, and possibly detrimental, to sketching existing environments.

Sketching is a continuing source of learning rather than a string of performances.

Writers and musicians know well the importance of extensive reading for successful writing or extensive listening for musical composition. Likewise, visual artists... understand that successful artistic creativity depends upon extensive visual exposure.

Please yourself, not others... It must first work for you if it is ever to be useful to others.

With pencil there is a tendency to be timid, either using very faint lines or erasing bad lines... Line sketching tends to emphasize the structure of a drawing rather than the nuances of media.

Focus on the opportunities, not on the constraints.

Sketching on a regular basis requires you to pay close attention to the visual world around you. With practice, you begin to see things you never noticed before.