This is a rather short post but I'm expecting long replies. If you enter a room where the marines have setup various structures, what are the structures that should be destroyed first? List the known structures in order of importance. (I want to jump in the game with a solid foundation, lol).

The Infantry Portal.

The CC.

Any turrets.

Those three are interchangeable. After that, go for the Armory. After that, go for whatever you feel like.

CC is wut? tell me how they all loock like!

Quote (L0G4N @ Oct. 29 2002,20:52)

CC is wut? tell me how they all loock like!

read the manual.

CC = Command console, and I second Necro's notion. RTFM!!

Heres what I would destroy only the top three though...

Any turrents (Unless they can't attack me while I'm attacking the other two I shal now list.)

Infanty Portal

CC

Sometimes if the marines aren't in the base you can take out the CC, just make a run past the turrets and position yourself on the opposite side of any turrets around it and chomp away. This won't work if the commander is smart/experienced enough to know that you should build 2 turrets on either side of the CC, or if the marines run back/distress beacon back to base. Also the CC has a load of HP so this works best when you have multiple aliens there, this almost always won’t end the game but it can force the marines to relocate (and they can be picked off easier while building a new base).

I always go for turrets first, unless I'm a level 5 or a level 4 with a bunch of support from teammates.  After that I kill off infantry portals and phase gates to keep the marines out.  Then I'd say CC's(the fewer the marines have, the better), siege turrets (to allow builders to set up support structures nearby), turret factories (keep the marines from expanding), and observatories (to keep from being detected).  It's also a good idea to destroy resource nodes immediately once the threat is gone -- the sooner you can destroy it, the more resources you deprive from the marines.

If you can do it without taking too much fire and have the time, take out the CC first.  Without a CC, the marines are in for a very, very short game.

I usualy have a priority list of CC>IP>TURRETS.

It depends however, on a number of things.  Such as number of turrets, placement of turrets and players in the area.

I agree with silverfox go for the CC first.

Monse or Fam above all, the, who cares

CC first - without a CC, there can be no more IP or turrets.  Only take turrets if they're preventing you from hitting the CC.

Once the CC is gone, then the IP.

For taking out the CC, make sure no one is nearby.  The commander will usually be too busy to notice his cc is being chewed on (sometimes he will but he'll most likely have a LMG).  However you'll alert any marines nearby.  If a marine dies, go quiet until you hear him spawn and leave.  Then continue.  

I usually go for the CC first, then turrets, then ip at the marine base.  For fortifed areas (like hive rooms), take the turrets out (remember to use the factory for cover! first, then the factorty or any portals.

Well even noob commander should notice when killing he's cc when he hears things like: "your command console is under attack" and what comes on priorize i would say IP -> CC..dont you think that after that game is over allready?

Definately the CC. I was just played caged (I think that's the one), and I used a lerk upgraded with adrenaline (a MUST have) and carapace to take out the CC. All I did was fly through the glass (I broke it previously), drop an umbra on the CC, and then I proceeded to bite it to death. To make this absolutely perfect, I went back up the vent (in the main marine base) then used the movement chamber that I built there earlier to return back to my hive. Then I sat back and watched the marines pee their pants because of their lack of a commander. Satisfying

I can tell you right now how effective destroying the CC is during the game. I was just playing on a great server last night. (Fantastic teamwork on both sides.) Our hives kept dropping and we were playing a shell game with the marines to keep them busy. This distracted them enough to allow a brave little skulk (I forgot everyone's name, it was late.)
to destroy the CC. This was the only CC in the game at the time. This left the marines in a defensive position: No new turrets, no new resources, no guns, no ammo, no health. Needless to say, we won.