Just a few thoughts...
I think it is better to focus on quality accounts- not a specific number. Decide what areas you can make the most money in and go after them any way you can- all the ways listed above.
Done properly, and depending on where you live, Craigslist can bring lots of quality work. Tonygreek has posted extensively on how to properly use it.
Look into Redbeacon.com, Thumbtack.com, and ServiceVines.com.
I have never done the door to door thing over large areas, but I will knock on the door of neighbors of existing clients. There is just too much profit available to not try it.