Competitive matchmaking in Team Fortress 2 has been in the works for quite a while, so much so that it almost felt like it was never going to arrive.
But Valve has moved one step closer to implementing a model that's hopefully similar to what has proved so successful for Counter-Strike: Global Offensive. That step is the opening of a Steam group that will be used "to send out announcements related to the competitive beta as well as seed beta invites for the expansion of the closed beta".
If you want to get in on the action, there's no prerequisites for doing so -- simply follow the link above and join the group. Whether Valve decides to implement any restrictions or qualifications on who gets invites from there is another matter. But for now, all you have to do is join the Steam group, something anyone can do.