Some stuff for commanders:
Going MT first can be really helpfull as most aliens-team tend to go MC first on good publics.
MT will counter those nasty silent skulks and will help ninjas getting pg's up.
With good marines MT will slaughter most skulks without leap (early game).
If alines go MC first and get an second hive up and you wanna attack a hive. Always go for the hive with the MC in it! Chances are good that aliens won't have an MC up at the new hive so they can't use them to get to the hive that's beeing attacked.
NEVEr EVER build buildings for upgrades if you don'T have the res to use them. I see it happen soo often, commander drops 2 ip's, obs and amrslab and roundstart. The obs can be used to scan (well most commanders don't know that) but the amrslab sits around the first minutes just unused.
Don't build 2 ip's at roundstart! Better use those res to get MT or the first lvl1 upgrade going. You can build the second ip when it's needed.
Get an backup observatory outside of base at the first location you secure (hive or dbl node) to do silent beacons. Silent beacons are a really good way to kill fades/oni.
When the pg and the tf at an outpost goes down RECYCLE THE TURRETS ASAP. They bring in decent res.
If a ninja pg to a hive gets up, don't drop the shotguns just when the pg is up. Most public players will hump the armory first before phasing so you are wasting time. Drop the shotguns at the same time as you drop the pg to the ninja. If the pg is up and you still got ppl humping the armory drop ammo-packs on them, most ppl realise "huh? the comm drops me ammo so i can phase to kill that hive".
NEVER EVER recycle a running resource tower when it's attacked. If you recycle it the skulk will most likely run off to the next one to bite it down, and in the time it get's recycled it doesn't bring you res in. Just let them bite it down so the alien-team has 1 skulk less to attack marines.
SC first is the easiest chamber to counter! I don't get it why so many comm's fail at that. It's really simple. Scanner sweep is your best friend! Bind your obs to a Squad so you can select it from anywhere on the map to scan. Get armor1 soon, and most important of all GET 2 HIVES LOCKED DOWN. Elec your resnodes that are farthest away from base. Build obs at dbl nodes and in the locked down hives.
If everything goes well you will end up with 3 observatorys and 2 secured hives.
Now work on getting back res on the map while getting upgrades and farming the hives. Elec every node. And KEEP SCANNING. Just a hint, you can scan even when teching phasetech or mt, select the obs and every few seconds the research bar goes away for about 1 second and you can hit "A" to select scanner sweep (needs some good timing there). After that it's just waiting for enough res to get your whole team into HA/SG.
Drop ammo-packs, drop them often and drop them well spaced and not just all on one place. So the marine can collect 2 packs for his lmg and 1 for his pistol. Drop some ammo every now and them.
Drop mines and welders now an then, somethimes you are lucky and some usefull guy will get the welder and weld all weld-points on the map and even stay alive to weld the armor on his fellow marines back up.
That's just some random stuff for commanders out there.
Let's go over to the standart grunt out there who get's the real work done:
Learn how to move, learn how to be silent. Aliens can hear you switiching weapons, so don't do that if you try to sneak.
Learn wallstrafing and doublejumping and all the other neat moves, they not only help you to dodge better but they also help you to move faster around the map.
Use your minimap! With it you can see how many restwoers your them has up and running. If you see that the team is low on restowers go and get some back!
Don't hump the armory until your full with ammo. First off all you will be moving slower when full on ammo. And second while you hump that armory the phasegate could go down
NS is mostly about res-control, so go after alien restowers! Without an weapon upgrade just knife them. If you got weapons 1 or better shoot them down. If you get killed while doing that just spawn and run back to finish your job!
If you get an weapon that'S worth res (shotgun, HMG, GL, welder) DON'T RAMBO. Allways stick with atleast one other marine so he can pick up the weapon in case you die. Allways try to keep weapons, for example: You got an shotgun and there's an hmg on the floor dropped by the poor guy who got killed. Just drop the shotgun and get the hmg. Repeat that until a fellow marine comes by to take the weapons. NEVER let a weapon disappear!!
If you got an HMG never EVER shoot any structures! HMG only does half dmg vs structures! HMG's are there to kill alien lifeforms. For killing buildings like hives/chambers shotguns/LMG and GL's are better suited. So cover those ppl with shotguns! don't waste your ammo on buildings!
If you like to rambo and want to be still usefull for your team there are some things you can do:
1. Get restowers back
2. Get alien restowers down
3. Rush a hive of your choice and kill the MC in there
ALLWAYS go for the MC!!
This can really save rounds, if the rest of your team goes off to siege/rush an hive you should go for the other hive and kill all MC in there. So aliens can't use them to "phase" to the hive that's beeing attacked by the mainforce.
Just shoot the mc down, 2 clips of the lmg and 1 pistol clip should do the trick.
If you want to get a ninja-pg up at a hive USE YOUR SCOREBOARD. The scoreboard is the ninjas best friend. With the scoreboard you can see if there are any aliens waiting to spawn. If you're next to a hive and there's 1 death alien just hide in some corner and wait for it to run past you. NEVER build anything at a hive when there are aliens waiting to spawn. Most likely they will spawn and hear you building.
If aliens got 2 hives up, the spawn changes from hive to hive. So if you just heard a alien spawn in the hive you are near the next one will spawn in the other hive.
If you are alone in a hive and no aliens are death there are a few things you can do:
1. Build a pg for your team.
2. Get ready to spawncamp them (not a good idea with a fade running around or another hive up)
3. Knife/shoot the node down (this one is real fun it works pretty often in early game)
4. Go for the chambers, if fades are around try to damage all the chambers at once so you can kill all at once in around 5 seconds. (this is something to **** fades really off when they sudenly loose all mc/dc)
The key to kill fades is not big weapons it's teamwork!!
For example: It's early game aliens got MC first and got a fade raping your team.
As the fade got mc he need's to get back to hive for a heal or find a gorge.
So what you gonna do is position yourself between the hive and the main force of marines.
When the fade hits the squad of marines he will maybe kill 1-2 of them and needs to heal after that. So he trys to get back to the hive. That's where you wait for him! Position yourself in some long hallway between the mainhive and the second hive. The fade will pass trough there very damaged and with luck you can take it down. The minimap helps greatly with stuff like that as you can see where the fade is attacking other marines.
Another good method is waiting outside marine-spawn. Most marine bases have 2 exits. A fade attacking MS will attack the base and when getting low on hp he will leave the base trough 1 of these ways. Now you need to have some patience as the chances are 50/50 that he will leave trough the way you are camping.
Against most medi-core fades this works pretty good as they only leave when they are REAL low on hp.
Against good fades this works not so good, but hey there's not that much that could stop a good 2 hive fade at all
So this is it for now. I hope my bad english isn't that bad and i could still bring most of my points trough ^^
If any of the above is unclear, feel free to ask about it and i will try to explain it somewhat better