Some of the items I will be adding in this tips post will be linked from other sources while some of this will be placed in a way that applies to new players specifically. I hope if you are new to the game that this helps take some of the stress out of the way.
The Newbie Help Guide - http://www.sindome.org/help/newbie/ Read over this, hell read it a few times as this will give you the basics to get on the ground running in Sindome.
Some tips for everyone - http://www.sindome.org/bgbb/open-discussion/anything-really/some-tips-for-everyone-205/ - Another one to seriously read a couple times, there is a -lot- of great information here for both new and veteran players alike.
@rules - Ignorance might be bliss, but knowing the rules of the game will make life easier for you.
help theme - This really does give a good idea of what your getting into.
Tips that are good to know (some reiterated for effect)
-You (the person looking at the screen) and your character (the person in the world of sindome) are not the same person, and that goes for the other person and their character. If someone does something bad to you, their character (not them) likely had a good reason for it. If you think something was fishy about it, before trying to complain, take a look back at your own actions and think if something you did might have sparked a consequence.
-Treat EVERYONE (PC or NPC) as living, breathing entities in the game. Just because a GM may not have the time to puppet an NPC doesn't make them any less motivated or affected by what you may or may not do to them. If you don't believe me, go up to gold and tell an NPC judge to suck it and see where it gets you.
-You are not a badass.. let me repeat this, you are -not- a badass when you come out of chargen. This is covered in the tips link up above but you really do need to get this. If you're coming out of chargen saying your character got a PhD in something, don't say I didn't warn you. Start off thinking small and work your way to being big. Nothing in SD (not unlike the real world) happens over night. Develop your character as you learn the in's and out's of SD and work towards being that bad ass.
-This is not a single player RPG, there are no definitive guides on how to do something. There is no real right way or wrong way to do things in SD, some people stray very far from where their character started off when they first came in the Dome. And there is no way to win the game, so enjoy roleplaying your character and have fun with them, seriously. The stats, while they matter, only matter second to the experience you provide yourself and other players.
-Don't get angry or feel like we're being asses when we tell you to "Find out ICly." Not everything is meant to be explained as some things do need to be discovered in the game. The Staff is very generous in the newbie guide to get you started on your feet, and beyond that much of what you will discover in game will be by RPing or your own discovery. At the same time, don't be afraid to ask questions but don't get angry if we can't give you the answer.
-Patience is a virtue.. Not everything happens overnight like I said, so some patience goes a long way. Can't run any packages? Try finding someone to RP with if your character isn't anti-social. You never know what can come out of a RP session with another player.
-Keep at it, even when the cards don't fall in your favor. Not every day can be a good day where you move forward, you will have days, sometimes several in a row where bad shit might happen to you. Just because it does, doesn't mean the world is out to get you.. Lay low, try and find ways to work your way back up and hell even work out a plan for revenge if you want. Half the fun in the game comes from the inherent conflict that can be found on a day to day basis.
I hope this helps with the new players that are in game. I know it can be a bitch starting out, but keep with it and you never know, your character's name might be one of the names that gets whispered in the dome for years to come.