what does "pull on his bottom lip"mean?
Sometimes, Eli thought, the way to get information was to give it. He did tell.
Stoney pulled on his bottom lip and considered. “What the hell could you bury in that basement? The floor’s as much stone as dirt.does that mean "drink up all the beers?"

Question

what does "pull on his bottom lip"mean?
Sometimes, Eli thought, the way to get information was to give it. He did tell. 
Stoney pulled on his bottom lip and considered. “What the hell could you bury in that basement? The floor’s as much stone as dirt.does that mean "drink up all the beers?"

Answer

Individuals have personal habits.

They do different things when they are thinking about something. Some people scratch their head. Some people tug their ears. I chew on my tongue.

He is "considering," i.e. thinking. His personal habit when he is thinking is to pull on his lower lip.