Relationships aren't always easy. But if cats and dogs can make them work, so can the rest of us. In Frenemies , the new book by creative partners Kim Levin and Christine Montaquila, we get an inside look at how our furry domestic friends manage to coexist on the same planet--even in the same house--and to live happily ever after. "Only count your own calories." "Learn the twelve steps of shutting up." "Remember their birthday. Forget...