In League of Legends, you can spectate all your friends' games after the champion select is over. Simply right-click on a friend in the friends list and click Spectate (in the League of Legends client).
In Counter-Strike, spectating via GOTV is only possible for Admins and Casters.
Spectating in Dota 2 and PUBG is only possible for Admins and Casters as well.
Spectating is available in some other games to different degrees, if you want to spectate a game or want to enable casters to join lobbies in your tournament, please contact our Support Chat - they'll help you out!