Use the bathroom across the street at the mall or at the "gates" for Amtrak, not the main waiting area. All other ones were built on hobo burial grounds.
Walk with the crowd, meaning with purpose. I hate when people who have no idea where they're going stop at the top of the escalators blocking everyone else trying to get through
buy your ticket last minute while standing in line, but use your iPhone to do it. sometimes they have empty seats on bookedbuses and you can skip the line.
The Main Gate Area is seriously the worst place you can wait for an LIRR train here if you actually want to get a seat. You are better off waiting by the Central Corridor (by Kmart) or anywhere else.
Penn Station is the major intercity train station and a major commuter rail hub in New York City. Serving 300,000 passengers a day at a rate of up to a thousand every 90 seconds, it is the busiest passenger transportation facility in the United States and by far the busiest train station in North America.