Aside from simply doing a Google search for a walkthrough, you could go to the 'Games' tab at the top of the Telltale page and click on the game in question. Telltale has provided walkthroughs for some of their games and can usually be found near the bottom of the game's page.
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For example: Sam and Max - Chariots of the Dogs
http://www.telltalegames.com/samandmax/chariotsofthedogs
Monkey Island
http://www.telltalegames.com/monkeyisland