Advice for both seats. Do not be a smart ar$e. Do not pre empt. Do be on time. And shave or grow a beard (ladies exempt from both). Sloppy appearance equals sloppy pilot.
A good Captain will let the know-it-all in the RHS dig a big hole, then bail him/her out. Never say “ I told you so”.
Let F/Os play with the FMS - they are better at that than you, BUT if their hands hover over the gear or flap levers, smack them. Just because Mummy and Daddy never smacked them doesn’t mean you shouldn’t.
But when it is the F/O’s sector, unless they are about to kill you, leave them to it. Nothing is worse than a line captain who turns every trip into a check ride.