I've been thinking for a number of months now how to do exactly what it says in the post title above. As a result, I have been subconsciously adding a mix and match of tasks into all of my recent lesson plans. Just take a look at the example lesson below...
https://www.bookwidgets.com/play/t:g-AtulkM59GWzr_Llej1pKUM3JDfGRzJu8DOksfBKtFLRTgyUktF
Then suddenly, I watch the video below and it all makes sense. What Luis Von Ahn is doing with Duolingo is exactly what I want to do with my lessons. Take a few minutes to check it out and I'm sure you will be inspired too...