Your CS:GO Trust Factor is the main method of matchmaking in-game beyond your rank, a system which looks at a multitude of elements before deciding what kind of people you’ll likely have a good time with in the game. It helps a lot if you’re fun to play with, but there are a few things you should keep an eye out on if you’d like to keep your score high.
Prime accounts are still a thing and having it enabled is definitely a bonus. The number of games on your account is also factored in: cheaters and smurfs will likely only have CS:GO in their library to limit their losses when they are caught. Similarly, having a lot of friends and an active presence in the Steam community – preferably with a high profile rank – will also increase your Trust factor.
Your time spent with CS:GO also matters – both over the course of the last two weeks and your overall playtime is looked at – and the in-game recommendations (or lack thereof) are also factored in. Crucially, the amount of reports you get can also make a dent in your Trust Factor – not just the odd one here and there from salty opponents, but if you are consistently considered a cheater, that’s probably not a good sign.
The exact details are shrouded in secrecy, and that is entirely on purpose: Valve will not reveal the specifics of CS:GO Trust Factor in fear of letting people game the system, while also allowing them to tweak a few things without having to publicize it. Still, paying attention to the points above and generally being a good teammate will help you go a long way.