What is it that Jim "often" does for Huck while on the raft?

I'd say that Jim teaches Huck life lessons and protects him, even it means his own freedom. He talks about what his family means to him. He speaks about survival and what is important in life. Jim acts as a lookout and patiently waits for Huck when he goes ashore, even when he knows he might get caught (which he does).