To dream of your grandfather may represent your conscience in situations that you have previous experience in. Your ability to make a decision or choose between right and wrong when you already have previous experience.
Alternatively, a grandfather may symbolize wiser choices or experience that overrides your own decisions. Grandfathers may also represents decisions made for you by someone smarter or more experienced than you. A decision to stop what you are currently doing because you feel it's in your best interest. Being objective about your own bad work or poor decisions.
Example: A woman dreamed of seeing her Grandfather showing her some beautifully crafted bookcases that were empty. In waking life she was beginning to think about making the decision to stop putting off her ambition to write. The Grandfather reflected the overriding decision to change her life towards writing from her current life.
Example 2: A man dreamed of walking with his grandfather and having a conversation. In waking life he was trying to decide what educational path he should take for his future. He was considering what was really best for him and what strengths would be best to develop.
Example 3: A man dreamed of his Grandfather screaming at him to wake up. This caused him to actually wake up from the dream. In waking life he had a serious medical condition that could kill him if he fell asleep for too long. The dream may have actually been a metaphor for experiencing God making the decision to wake him up from sleep to save his life. In this case the Grandfather would metaphorically represent God making the decision to wake him up, overriding his stupid decision to allow himself to fall asleep.
*Please See Grandparents