I occasionaly cant join games

Hello, I need some advice about my league client. This has happened to me a few days ago, and again now, where my game wont start after the champ select. Theres just a black screen for a few seconds, and then an error pops out, "you have lost connection to the server" or something like that. Last time it fixed itself after a few hours, so I believe it will be so this time too, but I wanna know how to fix it permenantly. Thanks