Only small pieces of advice I'd give for people doing observation flights is: Check the flow board for a shorter turn (like ORD-GRR, GRR-ORD) since the cruise time won't give you many insights. If you're CRJ, try for it in the 700/900. CRJ Jumpseats these days, with winter pax weights and winter weather alternates, make it hard to have a JSer and stay within weight and balance.

We were told (May 2021) observation attire is business casual or uniform, same as JS attire, but may have changed. List like you would for the JS, introduce yourself to the crew, ask the CA for a ride and explain you're doing observation flights for training. Everyone should be cool with it.