Agree that the first course of action is to see if the colleges you are interested in even care about demonstrated interest.
Visiting is the best way to show interest but it is not always possible. In addition to the above ways you can express interest in a college include:
-Email your admissions rep - but only only if you have a question that cannot be answered from reading the website.
-If there is an online admissions chat you could take part in that
-If the college interviews you could interview on campus if you get there or ask if you can arrange for an interview with an alumni that lives near you.
-If a rep of the college comes to your area you can attend the presentation, college fair etc.