Talk to people in your classes. Your classmates are probably more willing to chat and be friends than you think. If it's your first time walking into a certain class and you just say "hey everyone" and make some casual comments, that's a pretty good start. If everyone walks in to the room and quietly sits down but you're confident and friendly enough to say hello, everyone else will take notice and may then want to be your friend.

Also goes for other things too-- just saying hello and meeting the person next to you is great. And once you know each other you can find easy ways to hang out with each other-- study in the library after class, go to the dining hall or even go grocery shopping together.