Here are some things i think every person who is just getting into Linux or any other Unix-like OS should follow. Feel free to post additions to the list.
* Use root only when you have to. The root account has full control which makes the scenario that someone got access to root very very bad. After install if you havent already make a regular user account for non-adminstrative activities.
* The Internet is dangerous. This actually goes for any OS that you need to be careful with what links you click. "Think then click"
* Learn how to setup a personal firewall. Firewalls are a first line of defense in network security so read and prosper.
* Make good passwords. Here are two examples of a good password: R@cg6!Wge56 l03wRe7$ek <--notice how there is no dictionary words(leeting up words doesnt help) or how i use UPPERCASE and lowercase and numbers/symbols. Also you should change your passwords at least every two months. A good way to make secure passwords is to look inside a book, find a sentence, use the first letter of each word then changing some letters to numbers and symbols so you can just recite the sentence in your head to help you remember.
Orpheus said: Use root only when you have to. The root account has full control which makes the scenario that someone got access to root very very bad. After install if you havent already make a regular user account for non-adminstrative activities.
In addition, if you have multiple users using the server I would recommend not giving the root password to any of them. If you want them to have root privileges add them to the sudoers file instead.
And for total newbies, spend some time reading about the basic commands and permissions, and try to do everything through the terminal even if it takes you more time at first.
try to do everything through the terminal
And to that end, it is good to know that X | Y will redirect stdout from X to stdin of Y; X > Y will send stdout to the file Y and create that file if it does not yet exist; X >> Y will append stdout from X to the end of the content in file Y, which is created if it does not exist.
ln (a command for making hard or symbolic links) is better than porn.
If you su to root (or any other user) and want back to the one you came from, use exit instead of using su to get back, otherwise someone can exit back into root. Sounds like a trivial thing to warn about, but I've seen it happen.
Learn what file permissions do and learn to judge which file needs which permissions.
Oh and for the love of god, don't chmod a-x chmod.