Choose for the journey length
Balance sleeping needs, daytime seating, privacy, air-conditioning and budget. The same class can feel different on an overnight journey and a short daytime trip.
A layout is representative
Coach diagrams help identify common berth patterns, but the actual rake, coach series and accessible fixtures can differ. Check the final coach and berth on the chart or ticket.
Board using the final position
Coach position and platform can change. Recheck the station display and announcement, especially close to departure.