For many people, including myself, the Metropolitan Opera is opera's Mecca. I make a pilgrimage there every year. New York is a great city to visit for a mini- or complete vacation, and combined with attending an opera at the Met, it is sublime. Thus, it is worth noting that as of today, you can purchase tickets for individual performances at the Met for next season. You can view the list of productions here. Overall, with the exception of a new opera, The Exterminating Angel, it is a pretty standard line up. So, you might want to look closely at who the singers are. For example for La Boheme, you can have Angel Blue singing Mimi on Oct 2, 6, 9, 14, 19, 23, and 27, or Anita Hartwig on Nov 1, 4, or Sonya Yoncheva on Feb 16, 21, 24, Mar 2, 7, and 10. Likewise for Musetta, you can have Brigitta Kele on Oct 2, 6, 9, 14, 19, 23, or Susanna Phillips on 27 or Feb 16, 21, 24, Mar 2, 7, and 10. Ms. Hartwig is great, but personally, I'd really like to catch Ms. Yoncheva live. I'm not familiar with Ms. Kele, but Susanna Phillips is can't miss. Check carefully not only what opera is playing the dates you want to travel, but also who the performers are for that date!
If you need help selecting an opera to attend, Met Opera offers a web site quiz to provide you with some insight as to what operas might fit your taste. The best seats and the cheap seats tend to go fast, so act as soon as you can if you plan to make a trip in the coming year. The Met advises that the best way to purchase tickets for the 2017-2018 is through the Met website. You may also call 212-362-6000 for assistance. If you happen to be in NYC and can make it over to the box office, you can save a few bucks on fees.
The Met Opera HD in Cinemas 2017-2018 broadcasts have also been announced, and the list can be found here. Tickets for cinema showings do not go on sale until July 19. Perusing the list might help your decision of which to attend at the Met itself.