Break out into groups of two, based on the language you want to work in. You don't have to be at the same level of fluency, in fact, often it's better if you're not.
The first step is to code something with your partner, it could be generating the Fibonacci Sequence, or something as simple as "Hello World." Then, the real goal is to refucktor the code so that it still passes a test, but is hard to read, inefficient, unnecessarily memory intensive, really the impossible-to-maintain sky is the limit!
After each small change, run a test to make sure it's still working. This could be a test you run with a testing environment, or just printing the result of the function and seeing if it throws an error.