Since I've been told that I'm a good comm, I fell I can give you some decent advice. Comming in NS is much like winning in any game. You must be flexible. A large part of decent comming is getting a feel for how your team plays. You should know the all-stars, the ninjas, the nubs, and those who can follow orders. Then you need to put them to work. Avoid saying "one person" phase, build the rt, do something. Use his name to ensure that three people don't think that they are that one person.
Another thing is that you need to constantly know what the aliens are doing. Watch the game time when you play aliens and note first fade, lerk, hive, anything map specific that is important (such as how quick it takes to reach res nodes from hives). You should never have 100 energy in your observatory. Ping hives for ninjas, check lame at choke points, and other goodies.
Meds and ammo. Meds and ammo. These make or break a comm. Guns are useless without ammo, and meds can enable that marine to kill more skulks and save the res. Know when to med spam. Once as a fade I kept slicing at a marine only to have the comm drop med after med on him while his buddies blasted away with shotguns. Med spam is also needed to take down gorges and run past ocs. Keep in mind that ammo and meds cost money, which brings me to res.
Res is the lifeblood of your team. From it comes victory. You should always be on the prowl for res nodes. Use res responsibly, if you have excess res hand out equipment.
Final point defense never wins. You must be on the offensive and build momentum. I tend to do a very cheap lockdown with a pg and mines and instead of turrets or electricity (40 res!) I drop shotguns and welders.
Hopefully you can glean something good from that.