This would be a waste of time if the aliens have the middle hive. They'll just put the free hive up, and you would've wasted
time and res on locking down / securing a hive you don't really need.
If you have a lot of res, upgrade (armory, arms lab, obs). The armory should be upgraded asap. A second obs could also be handy, so you don't loose solely coz of a lone fade / onos that get's the first one. Give out guns and mines. Start pressuring alien nodes, and make sure you keep the ones you have by sending marines there as soon as they get attacked.
Turrets suck, use mines. Let's say your playing tanith, and aliens have satelite. Instead of laming up fusion / cargo with turrets, dump an armory and give out mines, shotties and welders. 4 mines cost the same as a turret, and have a higher chance of killing fades + you don't need to build em, only put em on da ground. Hope that your rines there don't get killed if you don't have Phase Tech yet

hf
edit - forgot my own personal strat. Rt's > 2nd Hive. Most important thing in a game is rt's imo. Get as many as you can, but more importantly, get alien rt's down. Getting 2 alien rt's down early game can be gamewinning. Make sure the 2nd hive doesn't go up. 2nd hive = alien win in 80% of the games I play. If it isn't up yet, get a pg in the hive if you can, and hand out mines and shotties. If it isn't possible to get in, or it's up and defended, siege. Have a player go out and recap rt's if you've lost some of them. Keep teching. Win