Make space. If you don't have a spare room, set aside a quiet corner for your office. You'll be able to focus better, and business visitors won't have to navigate strewn toys and discarded underwear.
Dress the part. Even if you're not meeting people face-to-face, mooching around in pants and a vest is unprofessional. Shave/take the curlers out of your hair, and then make the call.
Set working hours. The phrase nine-to-five may cause a cold sweat, but it helps to halt the drift towards brewing tea, watching Trisha and repeatedly vacuuming the same patch of carpet.