If it were a PCW then i use the opening minute or so to secure RTs. Once i have about 4 rts and a1 goes up then i'm looking to start pressuring alien rts. Generally 1 shotgun will be dropped to speed everything up and then I place a PG in the second hive before it goes up.
If i fail in denying second hive then i put down 3/4 shottys and welders and try and get a PG at a key junction, the rest of the team will then get hmgs and we'll push through to the hive location where the shotties take it down whilst the hmgs stop any fades.
If the PG goes up then what happens next depends a lot on the aliens. You can expect added pressure on your RTs at this time so defending them is a priority and recapping can often take several marines if their fades around. The aim is just to sit back and hold my RTs, tech up some more and hopefully kill some fades. If the aliens recap or drop a different hive then we push out and keep that whilst still holding our PG so we have something to fall back on before I push on the last hive.
My build order is: IP, ARMOURY, ARMS LAB -> A1 RT, RT, RT, RT. (Starting res gone)
Advanced armoury, a shotgun (maybe) weapons1, PG, obs.
After this i go for weapons 2 and MT asap.
Comming is a public is generally a less organised version of the above.