Git is just awesome and fast VCS, however, knowing better this tool will help you incredibly increase your productivity and save your time. Here we can try to make a collection of tips, tricks and useful links to better take advantage of git, this question can have some more sub-questions, I mean:

• what are some usefull commands that reverse or rectify commits/adding/removing mistakes?
• what are .gitignore & Global .gitignore best practices? especially with private/secure files that contains passwords, api keys, local config and so on ...
• .gitignore first or git add <files> first? what are the advantages/disadvantages of both being the first/last.

links to blog post, articles, would be sufficient. I thought every sub-question is not worthy opening a whole post each alone, I think centralizing these tips in one question post would help many people.