How To Ride Chicago's Metra

Chicago has three major forms of public transportation: the bus, the "L", and the Metra (the double decker trains that hold up traffic).
When I first moved to Chicago I was scared of the Metra because I thought my ignorance would hold up the train and the conductor would yell at me and all the passengers would give me dirty looks and make passive aggressive comments about me during the entire train ride.
I'm used to dirty looks, passive aggressive comments, and being yelled at, so I figured "what the h*ll, I'll figure the Metra out!"
Hopefully this will be of some help to other transplants that are squeamish about using one of the best systems of getting to Union Station without worrying about traffic and parking.