I don't write off anything that is jointly used by the business & the home - electric, gas, TV, etc. My accountant advised that the IRS look a lot harder at you if you work from home & do this, so I eat it.
But everything that's stand alone as far as a bill goes (phone, cable modem, etc) I of course write off.
Everything else that has to do with the business - computer, vehicle, hosting, independent contractors, cell phones, etc - is of course written off.
Some of the borderline things I shall keep to myself, but let's just say that anyone that's been to the house for a party, the business paid for the booze you drank
