Guess who has people bring him food and water, sits on the floor or a low place looking mournful, never cuts his hair or nails, and must be escorted when he leaves the house? That's right. My dog.
It's good to observe shiva in the home of the deceased, assuming the deceased had friends and neighbors who knew him or her. Not because "the spirit of the deceased hovers over his house" as is printed in some of the books, but because the visitors knew the deceased, not you. You want to hear stories, not questions, about the deceased; stories vary from person to person, while the same questions elicit the same answers until you're bored repeating them. Of course, it's good to be comforted by friends and neighbors who know you, too.
It's good to sit with two or mourners together, so that one can eat while the other fields visitors. When you're alone, if you get a continuous stream of visitors, you have to leave people milling about when you go eat.
It's good to publish the times that are appropriate for visitors, as well as a rest period during the afternoon or at mealtimes. Not that all of your visitors will pay attention to this. It's good to have a paper in front of you, turned to the visitors, with the correct mourner's greeting for those who don't remember it.
Don't sit all day; get up and walk around. You don't want a blood clot.
Synagogues or hessed committees should keep a box with siddurs, kippot, a book on mourning customs, the sheet with the mourner's greeting, and a checklist of customs and items to remember during shiva, to be loaned out to mourners.