It all starts with dedicated workspace.
Up here in the office, I have two desks. One is for the myriad of Ranch businesses, the other is for my computer consulting business. The wife & dawgs know not to disturb me when I'm at the consulting desk, unless it's an emergency. Compartmentalization is key in any home office.
Household business happens down in the kitchen.
 The cats even cooperate, at least for the most part. Go figure.