Did pretty well after my first few trys, I had the most luck going for early upgrades to weapons/armor while unlocking shotguns at afew armorys.
Had a really funny first game where I was being yelled at to make phase tech and didnt know how so I ended up laying the satilite dish thing right next to the guy asking for phase just to have him build and research right there as he fought off some skulks. Boy was he mad about that.
I think a problem that most marine commanders have is building a second base correctly, with infantry respawns and atleast the stuff for phase tech incase you lose your main. Usually commanders just throw the basics at second/third bases and then when main is lost you lose upgrades and all your tech, if you double up on those building you can really save the game.
Aliens I feel like always make atleast 1 second base correctly if not go for all 3 almost everytime. Which is a huge advantage if they push your main and get to those tech buildings.