This is the advice I would have given myself at 18: Don't fret girls and relationships. I'm serious. Focus on making friends (male and female), working on interesting projects, and learning everything you can (academic and otherwise) during the next 4 years. You may have inflated expectations of college women, assuming that intelligence and good behavior, decent tastes in men, etc. are correlated. I sure did. In fact…
Also, I guess it makes sense to say that college is like a clean slate - no one (well, mostly) really knows you, so it's a good time to reinvent yourself if you feel like it.
This is your chance to meet new people who have the same interests as you. Changing from a high school where very few people are interested in technology to a college where your entire program is filled with people who share your same general interests creates an awesome environment to grow and share ideas. The group of friends you meet in classes the first year can lead to an awesome experience in the second year, as you find people who you work well and agree with who will want to be roommates in later years. Can anyone say hacker house?