Now that school is in full swing (right?!!!) your school's college counseling office should share with you the colleges that will be visiting and when. Colleges tour high schools all over the country to either introduce or reintroduce their school to prospective students.
For the college admissions officer, this is a time to get to know the high school students since they will be reading these particular applications. As a student, this is an opportunity to become more familiar with the college to which you're considering or applying while getting some "facetime" with the person who most likely will be reading your application.
Here's what you should do.
Review the college visit calendar and make a note of when the schools that you're interested in are coming. If you have a class during that period, ask your teacher in advance if you can miss class to sit in on the session.
Do some advance homework. Go to the website the night before, this way you will know a few things about the school such as - size, geography, admissions statistics, standardized testing policies, and requirements -- so you can ask informed questions during the meeting.
Wear something pleasant and noticeable. If this one of your top five choices, wear something that you can refer to in a follow up email. Admissions reps are visiting 3-5 schools every day and will come into contact with possibly 50-100 kids in one day. There is a considerable chance that they will not remember your name. They are more likely to remember a distinguishable piece of clothing or a question you ask.
Your questions should be sharp. Ask about a specific academic program and how admissions consider applicants to that program. Ask about dorms and study quarters that are available besides the library. Ask about campus safety and how the students engage with the neighboring town. What are the nearby fun things to do?
Get their card and draft an email to say thank you. Try to highlight something you learned in the meeting and how appreciative you are of the valuable information shared. If it's one of your top choices, say so, but never say "you're my first choice" if it's not.