I added what and how I tip on my previous post, but it was an edit and you probably read it before I added it. I'll recap it, though tipping can be a fraught subject and opinions vary widely. This is just what I do. $10/night for the attendant for decent service up to $20/night for great service and zero for bad service. Done near the end of the trip. Tip in the diner by leaving cash on table. I tip fixed amounts that represent less than 20% of the meals value. Many will disagree with that, but Amtrak attendants are decently compensated unionized employees that needn't depend on tips for a living wage.

Operating crew, conductors and assistant conductors, are not tipped.