It's always infuriating to launch your League of Legends client, hoping to play a few games alone or with your friends, to discover that the servers are down — either because of patch maintenance or a sudden bug that has forced Riot Games to shut them down.
What's more frustrating is not knowing if the problem actually comes from the servers, or is on your side. Sometimes drivers need to be updated or reinstalled, and rebooting Windows is often the miraculous solution that you need.
However, before resorting to such measures, while raging in front of your black screen, there is something much simpler you can do: check the server status to see if they are online and working as they should.
If not, you'll just have to wait for Heimerdinger's tinkering to resolve the problem.
Keep in mind that maintenance is usually scheduled for the times when people play the least. For instance, Patch 10.1 was shipped to the live servers overnight, and unless you're an owl, you didn't even notice the change.