First off, thanks for taking the time to contribute!
Read on for more details in the Guide.
Include the version of Munin you are using and the OS.
Include screenshots whenever possible; they are immensely helpful.
Include any relevant logs; the mere act of writing a detailed bug usually gives the answer.
Include screenshots in your pull request if relevant.
End files with a newline.
Use the present tense ("Add feature" not "Added feature")
Use the imperative mood ("Move cursor to..." not "Moves cursor to...")
Use the standard commit formatting (look at the one already made)
Do your best to adopt the coding style already used in this repo