DO make it a point to interact with locals. No guide will give you as much helpful information as a local will. If you are not comfortable approaching people on the street or talking to that guy who just sold you a kickass souvenir, consider making a profile on Couchsurfing. There you will find tons of people who are willing to meet up for coffee and talk your ear off about their native city.
DON’T rush when purchasing your plane tickets. Even though you might think the airfare is down because of the lack of tourists some airlines will sneak in a ticket or two that are more pricy. Just like with your regular travel, come up with a strategy, set up website alerts, and snag that those cheap tickets away.
DO pick an awesome place to stay. The off-season will give you an upper hand when negotiating with your potential AirBnB host or hostel or even places you might pick on Bookings. Most places will have lower rates already but it never hurts to inquire about a possible discount. Who knows? You might even stay in some penthouse for half the price. So many possibilities!