As discussed somewhere else in this thread, I would strongly suggest joining societies. Societies are often the easiest way to make friends as you are all gathered together because of one similar interest or purpose. This equips you with some conversation topics already and you will tend to find that people come out of their shells a bit more when talking about something they are passionate about . Societies also have regular socials organised and are a great way to get you out of your comfort zone socially.
Usually societies do small taster sessions during freshers week so a good idea would be to throw yourself into those sessions and just show enthusiasm.
Getting to know your course mates is also a good place to start as you will probably have quite a lot in common with these people. You will go through similar situations (exams and tasks) and might have similar career prospects. From what I can tell quite a few people found their course a bit daunting when they first went to university, and sometimes this is because they don't feel they have someone to talk to or help them with their course. At the end of the day, course mates are the people that you are almost guaranteed to come into contact with throughout your uni life so some solid friendships can be made there. You can usually find course groups and chats on Facebook so if you aren't already part of one of them I would suggest joining one.
The truth is that the most people you will meet and chat to in freshers you wont even see again for most of the year. However that doesn't mean its not important to make the effort and interact with others during freshers week as it is the time where you all want to get to know people. I found that it was easier to make friends with people when I was being myself and being genuinely interested in what the other person was saying, then it doesn't seem artificial. If you aren't interested in the conversation then odd are you probably arent interested in that person and the friendship won't last.
You will find people at university who just simply won't put the effort into friendships or you might come across some characters that you don't gel with, when this happens just move on somewhere else. There are so many people at university and you will find the people you want to be friends with, you just have to look around a bit first.