"Consistency is clutch."
We'd jump rope as a warm up, then go into freestyle shadow boxing. We also did mitt work with partners. Being the mitt holder actually took just as much skill as punching it - if you don't hold up the mitts the right way, you mess up your partner.
In addition to my boxing classes, I also took two strength and conditioning classes per week. These consisted of mostly bodyweight training and conditioning, with a lot of running. By the end of the first month, I had lost around six pounds.