CH 17: The people changed locations to a place that had no water, and immediately complained about that. They complained until Moses cried out to the Lord for help. The Lord led Moses to a rock and told him to strike it, he did and water gushed out.
While they were camping, the warriors of Amalek attacked them; The Lord instructed Moses to have Joshua choose men to go fight back. Moses was to stand above them on a hill with his arms raised for Joshua and the men to defeat the Amaleks. But when Moses' arms tired and dropped down, the Israelites began to get defeated. So Aaron and Hur found a stone for him to sit on and they stood on each side of Moses keeping his arms up. At this point the Israelites regained the advantage and eventually defeated them in the battle.
CH 18: Moses' father in law comes to visit because he's heard so much about the Israelites and about the win of this battle against the Amaleks. Moses tells his father in law how exhausted he is taking care of all the cares, worries, and disputes of the people, and Jethro his father in law advises Moses to designate leaders for groups of the people (after making sure they understand all God's laws). Moses does this, and remains the ultimate overseer and it works out much better for everyone.