How does Priority Boarding work?

[stxSteve]

I’m a solo traveler using the RAILPASS that was on sale last month for a trip on the CZ, Chicago to San Francisco next Sunday. That pass does not allow upgrades from coach. Question: Is their anything I can do that would increase my chances of getting a window seat? Would it be worth the $35 for the Metropolitan Lounge in Chicago, I’ve got a 4 hour layover before boarding the CZ?

 

[caravanman]

I don't think there is any sure fire way to achieve priority boarding. Sometimes the "redcaps" take elderly or infirm passengers to the train first, but sometimes not.
Best advice is to try and get near to the front of the queue/line for coach boarding. Sometimes the car attendant will allocate you a seat as you board, just ask politely for a window seat.
You can sit in the lounge/observation car anyway to enjoy the views.
The coach line queues form at a different place to the metropolitan lounge, so it may not be an advantage to spend your time there from that point of view. I don't think there is much point in paying to use the lounge myself, benefits are minimal.
Have a good trip!