Start with putting your interests on here. Also, if you are talking a PE class, talk to the people that look like they actually enjoy being in that class. Also, enroll in classes that you're interested in and you're bound to meet people that share these same interests. The most important thing is "don't be shy". Open up. A lot of people are afraid to start a conversation...just be friendly, smile at people, say hi and start a conversation...usually with an open ended question, not a question that could be answered yes or no. Good Luck.
