You'll get this once the train is moving again
Talk to Chuck and he will suggest that you teach Clementine to protect herself and cut her hair so she can't get grabbed so easily. He will also ask if you have any drink, but you don't.
Head back to the box car and take the whiskey. Then talk to Clementine and teach her to shoot. You will need to pay attention to where the bullet hits, so you can tell her where to aim.
On the third bottle, she will hit it herself. You should then suggest cutting her hair.
Head back to Chuck and give him the whiskey. Ask Kenny if he wants to have some Whiskey and he will go outside to Chuck. You can then grab the map next to where he was sitting.
Go and talk to Clementine about Savanna using the map. Once you have a plan, the train will stop and you will get the achievement.