The advice of putting yourself in social situations is a start, but you also need to 1) be approachable, 2) be able to handle the social interaction, 3) know how to grow the relationship.
All of this depends on the type of social interaction, the people around you and will change over time.
For #1, I've noticed that people who are attractive or have a pleasant demeanor will generally have more social interactions initiated by other people, so at least make sure you don't hurt your appearance.
For #2, having a good sense of humor helps, as well as being able to have a conversation and relate to other people.
For #3, honesty, shared values, boundaries and timing is important. Here, like others have mentioned, you want to spend time doing various activities together.
Also, people can sense when someone's 'forcing' the friendship to happen, so try to not to stress out about it. You'll get direct and indirect feedback when interacting with other people, so learn to read between the lines.
When in college, you will cross paths with other people without a lot of effort, just make sure you take that first step of putting yourself in social situations, because it's only going to get more difficult as time goes by.
Lastly, friendship has a maintenance cost (both time and resources) and a dynamic between the parties, which may not always be beneficial for you. For example, my best friend in college was a great friend in the beginning, but as soon as he got comfortable with the friendship, he began to undermine me, push the boundaries and use the friendship to his advantage. I believe that's just his personality and as much as it hurts to lose your best friend, I had to cut the friendship for my own well being. I don't recommend breaking ties at the earliest sign of trouble, I only want to make sure you're aware that a friendship can end up being a net negative for you and you should evaluate the friendship once in a while.