How to build Ensemble Models in machine learning? (with code in R)

Over the last 12 months, I have been participating in a number of machine learning hackathons on Analytics Vidhya and Kaggle competitions. After the competition, I always make sure to go through winner's solution. The winner's solution usually provide me critical insights, which have helped me immensely in future competitions. Most of the winners rely on an ensemble of well-tuned individual models along with feature engineering. If you are starting with machine learning, I would advise you to lay emphasis on these two areas as I have found them equally important to do well in a machine learning.