In my recent posts I have talked about what Sitecore provides now out-of-the-box with version 8.1+ to support Language Fallback, an overview of Language Fallback, a How To on configuration, and the Questions you should be asking for your strategy.
Just knowing what the questions are you should be asking is half the battle! But I'm sure you would love a little insight into what some of the answers to those questions would be. Although every scenario is different, I can at least try here to give you some guidance based on my own experience and call out some good-to-know gotchas.
Sitecore Content Strategy
Sitecore Search Strategy: