There are 3 main types of parties at MSU - dorm parties, frat parties, and house or apartment parties. Dorm parties = typically freshman living in the dorms, super small/among friends, bring your own booze or sometimes the host provides for you. Frat parties = every freshman starts out going to these. Ton of people - at the beginning they give out booze, but eventually it's BYOB unless you know someone in the frat to provide you some. Meat market - I want to hook up or dance atmosphere. 10% of MSU goes greek so it is a noticeable but not huge population at all. If you are interested in going greek, go to the Greek barbeque (early on in the year) then there is rush week - you have to pay a fee I think, but you get to visit all the houses and see if the frat scene is for you (under no obligation to join one after rushing). You don't have to go greek to go to their parties, but past freshman year most greek parties get old anyways.
As for House or apartment parties - they are typically for upperclassmen, but I crashed a ton of these parties my freshman year (see lots of people on a lawn partying - go into house, drink their drinks - $5 cup for kegs is standard. etc. Talk to friends' friends - its always worth it to keep party contacts at the beginning - people that you don't necessarily like but you just text them on the weekends to see what they are up to/where they are going. Or creep on public facebook party invites...if they have over 100 people confirmed it is worth checking out past 11pm etc.). Shady but hey, that's what you have to do at first as a freshman not knowing anyone...yes, I did all of these things at one point in time. :P Fortunately, you eventually make friends who know friends or get actual invites to these. House or apartment parties can range from small-ish gatherings to being even more crazy than frat parties.
As for where they are, most of the frats are along Grand River by Woodmere, or in South Harrison. House parties are everywhere there are houses, but popular party streets include M.A.C., Gunson, Milford, Stoddard, Beal etc. Cedar Village/Americana are the most popular for apartments (normally need an invite/person you know to get buzzed up into those). Dorm parties are wherever there are dorms. In the freshman dorms (brody, hubbard) you are a lot more likely to get caught. Loud music is a main reason for these parties being busted, so if you are relatively quiet you won't get in trouble. This is a lot of info, but feel free to ask me for more details!