Best Means to get Cheaper Broadway (NYC) tickets?

[disfanforlife]

I might try to get tickets to either the Last Ship, Gentleman's Guide, or Honeymoon in Vegas when we arrive on Thursday, January 15th - didn't want to chance buying ahead of time incase the train was late. I did buy ahead for the other days that we are there. Really looking forward to If/then ( my first choice) and On the Town ( sons choice) and Jersey Boys ( mothers choice) haven't been to NYC in years so we are packing in as much as we can on this trip!