1. Forget about GUI and use command like for any single task,
2. Use man pages to learn more about commands and try many options,
3. Don’t rely on screenshots, go and explore config files such as /etc/lilo.conf,
4. Use few distros, test yourself extensively on both rpm and deb management,
5. Remember the paths to most important files fstab,inittab,etc..
6. Open yourself more to subject you think may be unrelated to you,
7. Don’t rely on books, check the objectives on LPIC website.