Changes to slides

thanks a ton, @sarah.diehl

2021/2021-03-18_basicGitTraining/slides/best_practices.md

 # Best practices
 
-* `pull` before `push`
+* `pull` before `push` and, generally, before starting to work
 * Work on your <font color="red">own</font> branch (in your own fork), and **not** on `master` and **not** on `develop`
 * Do **not push** to `master`, but **submit a Pull Request (PR)**
 * Get your code **reviewed** by your peers (submit a PR!)