After John's death, Dean spends his time fixing up the Impala at Bobby's place.
Bobby gives Dean advice to help him personally and on jobs.Bobby's house is like a home to Dean and his brother Sam Winchester.Bobby is a family friend of the Winchesters and they have known him for a while.Whenever John had a case, he would drop the boys at Bobby's and he taught them how to hunt.So, Bobby shows Dean and Sam some lore until Meg shows up.
While Dean is exorcising Meg, Bobby pulls Dean to the side and tells him that there really is a human girl trapped inside, and getting rid of the demon may kill her.
After Meg dies, Bobby tells Dean to go get their father and he'll deal with the cops.
Dean is concerned that Bobby may have trouble, but Bobby rebuts by saying do you think you invented lying to the cops?
Bobby also tells Dean to bring John by, and promises not to shoot him with buck shot.
Bobby is also a hunter and has stacks of books of lore on anything that is huntable.
There was one time when Dean was young that Bobby didn't do what John asked and took Dean to the park to play catch instead of practicing with rifles.