I prefer a "positive consequences" method. Call it rewarding, or even bribery if you want. If a member of my team does something that makes my job easier, I'll gladly refill the office candy dish & fridge with their favorites.
What works best though, is a listening ear, and undivided attention.
Today, I was running back from a very short break, while trying to juggle a move in, a tour, several urgent emails from my corporate office, and a vendor. My maint tech wanted to vent about the third laundry room flood in two days. How you prioritize these tasks can make a huge difference.
I closed my door, put down the move in paperwork, listened to my tech, and thanked him for cleaning the mess again. For two minutes of my undivided attention, support, and appreciation, he will be motivated to take care of all the dirty work again tomorrow.
My boss gives out awards at our monthly meetings. The certificates are free to make online, and she always finds something to give a reward for. So far this year I've been awarded with fancy looking certificates for 100% occupancy, pre-leasing, meeting NOI, etc. Giving something tangible, even if it has little monetary value, can still boost a spirit!