Probably a high school or junior high class, right? I've taught HS and currently teach university where some of my classes are even bigger (50-120 students).
So, #1, please tell us what grade the students are.
#2, what are you supposed to teach them? Writing? Oral communication? Speech making? Group projects? Reading skills? TOEIC prep? Etc.
#3, are you given a textbook? If so, what is it? How strictly are you expected to adhere to it vs. use your own ideas/supplemental material?
#4, what is the schedule you have to teach them? Once a week for 40 minutes? Twice a week for 90 minutes?
Basically, in any large class, you have to get them to work in pairs or small groups a lot. Not always, as this becomes hard to judge individual performance, and if students always work in groups, they may resent the fact that they can't do some things by themselves. To tell you more about what to do, however, I would need to know answers to the questions I posed.
Edit: Look up books by Penny Ur. She has written a few that give advice and lesson planning advice for large groups.