You should be able to beat a couple Hard AI in a free-for-all game (with Locked Teams so that they can't gang up on you, of course).  At a minimum you want to be familiar with the basic mechanics of the game--how to upgrade a planet's population, how to take neutral extractors (the ones in asteroid belts and around gas giants where you can't colonize).  Also, you should be comfortable enough with it that you know your starting moves so that you don't need to think about what to do at the very start of the game.  (Ie, Build a capital ship factory, order the building of extractors, order up your first (free) capital ship (should be a mothership that can colonize), roll out two or three scouts and start scouting around, then send the capital ship to colonize the asteroid.)

I also suggest playing with and becoming familiar with all three races and learning their strengths and weaknesses.  FYI, the TEC is the weakest faction and few experienced players choose to play TEC online.  (In other words, I suggest that you learn to play either Vasari or Advent)

If you can do all of that you'll be ahead of your average new online player.  I think that's really just about all that you can do to prepare for it since playing against humans is a very different game from playing against the AI.  I suggest investing in increasing the size of your fleet and NOT focussing on a long-range economy strategy.  (Trade ports won't help you when you're dead.)  Also, spend some time reading threads in the strategy forums.  When you come online you'll find a mix of skill levels from heavily experienced players to mediocre players and even new players.

Sometimes.  You can always ask if someone would put up a humans v. AI game (aka "comp stomp") which is a nice way to enjoy other people's company while you learn the game.

I rarely see anyone do it and I don't do it.  Best bet is to hit the can and get drinks and snacks before the game starts.

Unfortunately, no.  There is a win-loss record, but an experienced player could always just create a new player name and join the game lobby with a 0-0 record.  Those guys are called "smurfs".  I wouldn't get too hung up about that, though.  When you join a game, before it starts you can politely request that the teams be balanced if you see a bunch of good players all on the same team (or just take off before the game starts and wait for the next match to form).

Since it isn't an FPS ping isn't a huge issue.  However, it is possible that a single player could lag to the host and lag the game.  Sometimes it can be a problem.  The best thing that you can do is to try not to lag yourself.  Close all other programs and especially stop any downloads or anything else that uses bandwidth before you start the match.

There are a couple jerks out there but for the most part I think you'll be pleasantly surprised at how collegial most of the players are.  It's definitely not as bad as communities I've known for the first person shooter game I play.

Log onto Ironclad Online (not the Multiplayer LAN button) and come check it out.

One problem with the game is that sometimes it can crash resulting in a "Minidump" and people dropping out of games early-on as a result.  Another problem is that you probably won't be able to host games.  To host you need to configure your router for Port Forwarding (see the sticky threads in the Technical forum).  The 1.1 patch is going to fix the game so that anyone can host regardless of whether or not they've futzed around wtih their router.

Welcome to the Sins Online Multiplayer community.  I play as WHIPperSNAPper and DirtySanchez, so if you see me feel free to say Hello.

thnaks for the very detailed replies , that's been a good help . I'll give it another week off singleplayer (not getting to play much at moment due to work) and then try it online .