If you are already in the locale, nothing beats a face-to-face negotiation with the manager. We have a Residence Inn about 300 feet from our office complex. For a long time they were shy about giving us longterm rates.

One of our managers made an appointment and took the hotel manager out for a nice lunch. Made a world of difference. Not only do we get very good longterm rates, but we get to select the rooms we want to book (close to our building, newly fixed up rooms with handy parking etc.)