1) its only your 2nd year. just sit next to someone new in every lecture and do talk to someone. if the conversation goes beyond small talk then you know your getting somewhere.
2)socialising takes a lot of effort, usually the people who are popular are also clever at it. they will identify who is popular and then they will get to know them as well as the people they hang out with.
3) effort is a big thing. making the first move is the hardest part. make the first move and people will start respecting you for it. people who are popular make a lot of effort and thats what it comes down to (my opinion only).
4) dont take the view that 'its my 2nd im not gonna get to know anyone', i took that negative view and i ended up hanging out with all mates in my first year. a lot of people get to know each in the 2nd year. infact i got to know all the people i know from uni in my first year , meaning that i under-performed because my thinking was wrong. i know a friend who didnt live in halls in the first or the second year. however she ended up knowing people on our course because she thought to herself - 'ive missed out over the last 2 years, and im gonna make up for it'... infact she was the most well known person on our course.