The standard rules of the server can be found here.
A few things to note.
Modified excerpts from the gospel according to Jason:
1: Many players HEAVILY FROWN upon the use of the AWP. Many become GENUINELY ANNOYED. There is a discussion on the banning of this weapon here.
2: There are a handful of maps that we tend to play a lot. This is because they are GOOD MAPS. They have consistently proven to be a good size, balance, and level of fun and we pick them for that reason. If you are new and don't know any good maps when a vote pops up, ASK! Don't instantly press 1 just to make the vote go away, and don't repeatedly vote for Dust and Office. Don't vote for abstract maps every round because you are a nipper worshiper and you think they're the coolest thing ever, we tend to avoid them because they are quite large and without like 25+ people it makes for extremely long rounds and a lot of people sitting in spectator or wandering around the map trying to find the enemy.
3: Friendly fire is ALWAYS ON in the server. It's easy to shoot or even kill someone on your team by accident. This is fine, it happens all the time and is sometimes hilarious. HOWEVER several things involving friendly fire can be VERY annoying. If you come out around a corner and you're on my team and I shoot you and immediately say "Oops, sorry dude" over mic, don't empty your entire clip into me and leave me with 10 health and then say "YOU SHOT ME FIRST!!!" Same goes for getting revenge on the person that accidentally shot you and creating a cycle of TKs that gets you both autokicked.
4: Voice chat is a great thing to have and offers many good times and lols. Be careful about being the person that is constantly holding down your voice chat button. Having 10 people loudly and excitedly chattering at once can be a big headache. Type once in a while if you can't get a word in on mic because a lot of people are in the server. It helps.
5: If you need someone to change the map, try finding someone in our IRC channel. There are plenty of admins around who can help.