Yesterday, I posted that it isn't always necessary to visit a college because there are other ways of demonstrating interest if it's inconvenient to make the trip.
But if you really want to delve into how colleges make decisions, visit collegedata.com. Here's Villanova's page. They consider a student's interest, so it's a good idea to visit especially if you live locally. If you visit University of Indiana's page, you'll see that they don't consider a student's "interest" at all. If the school is your top choice, by all means visit and build a relationship with your area rep. But it's not a prerequisite for getting in.