Otherwise, Amtrak has a first-come, first-serve seating policy for coach seats. Essentially, you board the train and find open seats to sit in. If you are traveling with a large group, you can look for the Amtrak “red cap” service desk or staff wearing red caps who can help you find seating. Be sure to tip and connect with the red caps before your train arrives.
If you have booked a roommette or bedroom, you’ll receive your room assignment after booking your tickets.