Contacting faculty is usually fairly easy. Their email addresses and phone numbers are often publicly available on the school's website. You can also contact the administrative staff of a department to ask for contact information for a professor, which they are usually happy to provide. Contacting alumni may be a little more difficult - it's best to network through your friends and family to see if anyone has a contact they could set you up with so that you have a connection. If that's not possible, the admissions office might be willing to put you in touch with an alumnus.
In your communications with these people, the best thing you can do is to get information from them about the school - it's called an "informational interview." Try to find out if the program is a good fit for you and why - ask about the program's overall focus, the curriculum, the accessibility of professors, the location, the emphasis on academics v. work experience, and student life. Ask about how helpful career services is in helping students get positions after graduation. And ask about concerns specific to international students, like financial aid and other support.
More info about how to approach these conversations:
https://blogs.voanews.com/student-union/ ... t-talking/
These sorts of things can help you in admissions because you will (a) focus your applications only on the schools that are actually good fits for you; and (b) be able to articulate why that particular school matches your goals.
In general, as long as you are polite when you contact people, write in proper English (no text speak/abbreviations, correct capitalization, full sentences, etc.), and show that you are genuinely interested and not just trying to get them to put in a good word for you with admissions, they will be happy to take some time to help you out.
