What advice had Papa given Travis about hunting?

Readers can find the answer to this question in paragraphs 3, 7, and 8 of chapter 3.  Travis tells readers three specific things that his father taught him about hunting.  Paragraph 3 tells readers that Travis's father had taught him how to tie up a deer's feet together and pack it across his shoulders to get it home.  Paragraphs 7 and 8 tell readers the two important things that Travis's father told him about actually hunting the deer.  Travis's father stressed the importance of understanding how powerful deer senses can be.  The specific senses to be aware of are the deer's sense of smell and its vision.  Travis's father taught him the importance of hunting from a downwind position.  That way the deer never gets the hunter's scent.  The other thing that Travis learned from his father is the importance of keeping very still.  His father told him that deer vision is especially good at seeing motion.  If Travis can be downwind and very still, the deer will never know that he is there:

Then I made myself get as still as the tree.
Papa had taught me that, way back when I was little, the same as he’d taught me to hunt downwind from my game. He always said: “It’s not your shape that catches a deer’s eye. It’s your moving. If a deer can’t smell you and can’t see you move, he won’t ever know you’re there.”