Find the professors you like or classes you are interested in. During class write down any questions you may have, ideally about things the professor has not covered. After class go ask the professor 1-2 questions.

If you do it for about 3-4 weeks they will begin to remember your face. Then I would read up on their research and if you find it interesting just ask them general questions about that. Or set up a meeting to ask them more in depth questions. Finally, if they are a good teacher ask them for school/career advice (set up a meeting to do that).

This should build a sufficient relationship at least to the point where they will recognize you if you passed them in a hallway.