Hi,
If you know an alumni, that is a great starting point. I always tell my students to build up connections with target schools - it shows commitment and a great way to differentiate yourself. However, the biggest mistake applicants do is to just name drop. It doesnt help because the adcom will not verify that. What is important is what have you learnt from the alumni.
Ask them about the culture of the school, the support system, who is more likely to succeed, what kind of people benefit the most from the program, what are typical buzzwords, which classes are more popular - none of these will be available on public search/domain. Yet you can align your essays to discuss these points and ensure that you are portraying a story that makes you come across as more genuine, detail oriented, structured - all of which are great skills for your MBA.
Hope that helps,