Best practices of orchestrating Python and R code in ML projects

Today, data scientists are generally divided among two languages -- some prefer R, some prefer Python. I will not try to explain in this article which one is better. Instead of that I will try to find an answer to a question: "What is the best way to integrate both languages in one data science project? What are the best practices?". Beside git and shell scripting additional tools are developed to facilitate the development of predictive model in a multi-language environments.