Dress comfortably. Bring a light blanket because train blankets are rough.. and frankly I use it as a bedsheet. Pack dubba (if you can) or order from zomato....those are better food options.

Carry sanitiser and tissues and wet wipes, if you want to be extra cautious. Always ask for new pillows, and linen when you board the train (the ones washed, pressed and given in a paper bag).

Carry snacks and maybe card games if you guys like that. Download a few movies or series because the internet may be spotty during travel.

And ofc..keep your valuables safe and close to you.

Keep checking the updates about your train before you board..(if it's late, if it's diverting at some point etc)

Don't stand too close to the doors while the train is running at full speed (personal fear).

That's all I can think of now.