Title
Idealy, title should follow the commit convention as in this title.
Description
I describe my bug or my feature.
If this is a bug, I give my configuration and all the elements that lead to the bug. Then I give the expected behavior.
If this is a feature, I explain exactly what I want to implement and what is the need. For that I can write a User Story
Documentation and sources
If I have some images of the bug, a sketch of the feature I want to implement (if it is a graphical feature), a diagram of the solution I am thinking about, or other usefull resources, I can attach them to my issue.