Assuming you didn't fall for the carrot trap, your team tried their best to meet or beat the monthly goal. So what do we do now? Is it as easy as an "attaboy" and pat on the back? How much praise do you give without going overboard?
Well, depends on your team. I've known people to take their team out to bar to celebrate. Longer potluck style lunch with everyone bringing something simple. Individual "awards" for the work. Something that shows you are there and you too feel pride in their work.
See the goal is a group effort. You never get the best results when one person is supporting the weight of the entire department. While you will have over and underachievers, most will fall in the middle. Never forget you are leading by example and setting one starts with stepping in and participating.