Preparing the Drawing for an Oil Painting by Don Finkeldei: A loose, quick drawing on the canvas is better than a detailed drawing. Make your lines very loose.
I don’t worry too much about getting the shapes exactly right. It’s basically an indication of where I want to put things. Just indicate where they go without drawing the whole thing out. For instance, on buildings I indicate the roof lines loosely. I don’t draw in doors, windows, etc. One thing to note about doing line drawings is that lines make you subconsciously paint up to them sharply. You don’t want to do that. A painting works with masses and edge variation. A line drawing doesn’t use masses and edges so don’t make your lines so distinct that it forces you to keep sharply within them. That’s why a loose drawing is better than a very detailed drawing. Don’t worry about painting up to lines. You can refine the detail later.
Example of a preliminary sketch by Doug Higgins. http://www.dhfa.net . Doug also has a very good online book and is one of the best landscape painters in the U.S.