Amit at Red Blob Games has out up a lot of information over the years describing common algorithms for implementing hexagonal grids in strategy games. Red Blob Games is a highly regarded site for such information as well as other very useful game design concepts.
However, given that his information for hexagonal grids is quite in-depth and runs to rather long web-pages I have taken all of his documents and put them into a PDF file in the same order that Amit presents this data so that it can be printed for more relaxing reading.
You may download this document from the following link… Amit’s PDF Document