While the game isn’t out yet, Valve is giving out CS:GO beta keys to those who participate in an online survey. Keep in mind that doing the survey isn’t a guarantee that you’ll get a beta key, but at least you’ll be considered.
Hey, it’s better than nothing, right? Before you jump right in to take that survey, keep in mind that you need a Steam account and you have to allow Valve to “scan” your PC to know your system configuration.
If you’re a fan, I doubt any of these will deter you from signing up; and in that case, good luck!