Check your cable or satellite service provider. Many cable sites, especially for premium cable channels, offer the current episode for free; it's part of your subscription cost, but you don't have to pay to watch online. If the provider's website doesn't have it, check for a section of channels devoted to past episodes or see if the provider offers an app, such as HBO GO, that enable you to watch TV episodes on your iPad or tablet device.
Check fan sites. Fan sites for TV shows often license the current or past seasons to provide access to their fan base.
Check the network. ABC, CBS and other networks typically provide the current season's episodes online once they've aired on TV. Watch from your computer or mobile tablet device via Wi-Fi.