IBM’s DeveloperWorks has 10 Good Unix Habits, which apply to GNU/Linux at least as much as to Unix.
I would expect that most experienced admins can second-guess the content to 5-7 of these 10 points, just from the title (for example, item 1 is a reference to “mkdir -p”, plus another related syntax available to Bash users). I would be surprised if you knew all ten:
1. Make directory trees in a single swipe.
2. Change the path; do not move the archive.
3. Combine your commands with control operators.
4. Quote variables with caution.
5. Use escape sequences to manage long input.
6. Group your commands together in a list.
7. Use xargs outside of find .
8. Know when grep should do the counting — and when it should step aside.
9. Match certain fields in output, not just lines.
10. Stop piping cats.
How many did you get?