I believe that bullets are one of the most impactful features of recent versions of Coq, among those that non-super-expert users can enjoy. They had a big impact on the maintainability of my proofs. Unfortunately, they are not very well-known, due to the fact that some introductory documents have not been updated to use them.
Bullets are a very general construction and there are several possible ways to use them; I have iterated through different styles. In this post I will give the general rules, and explain my current usage style.