Offense:If you want to play offense at the start of the game, spawn at the very edge of your spawn zone, once launched push into the middle of the map as far as you can with the drop pod, in the first few seconds build a razorback station pointing to the other teams base. If you conserve time well enough there should be alot of guys just sorting out their defenses on the other end. Run over all of them before getting out and grabbing the flag and getting back to base. I would not wait for passengers unless they know what you are doing and are ready.
Defense: At the start let the other guys build walls as they will likely get run over unless they are careful. On Acid Sea I think walls aren't that effective at the start anyway because you need 6 walls to block the ladder and if someone lands on top with a hawk or jetpack even though they can't fly with the flag they can circumvent the wall by jumping off the side. The best initial defense is letting someone who is rushing on razorback come in and staying on top of the bunker, wait till he gets out and then get in his razorback or destroy it outright. If you want to continue playing defense probably turrets on top of the flag bunker and a supply bunker that faces up hill are very important. And then beam turrets to control hawks and then a shield.
TDM: The outlying bridges are essential for resupply of rift, build spawn beacons there, also there are mines in the very middle of the map (up a ladder and on a platform) which are also good to control with a spawn and then build a supple depot. Basically who ever can control the middle will usually win, as you can just continuously pick off spawners on the other team unless they've secured a good spawn at the bridges.
Offense: Very similar to Acid Sea in the opening razorback blitz method except this time the other team is wide open at the flag, you can circle around and around and usually get 5 kills before you get the flag as there is no pre existing ladders to jump up. There are barrels all over the place on this level as well and the mid point also is a good control point for the mines.
Defense: You must build a single wall and get up the ladder and assume there is a razorback coming, you will then have enough to build one turret and this should be covering the flag. Build your walls in a triangle using three facing inwards as well, yes the enemy can climb in but they then cannot climb out. the only way they can get out is with a hawk and then jumping or destroying the wall which takes concentrated effort.
TDM: Find a good place up top on the towers to lay a spawn beacon and build a jetpack dispenser, that way when you die, you can respawn by the barrels and then have enough rift to buy another jetpack. Really on this map the jetpackers will always dominate as there is so much verticality. You can stay up top and snipe or drop down behind people for backstabs. They've recently nerfed it a bit for fuel and recharge but it's still king.
Beam Turrets seem insurmountable when you are in a hawk. But you can get them with a high angle of attack, or more importantly get into a heavily fortified base for the flag. Get up as high as you can and divebomb the flag at 90 degrees avoiding surrounding beams, changing to mech mode and hopefully landing on the flag, you can't fly now you have the flag, but you can hop, get outside the walls and build a razorback garage and probably drive out unscathed.
Destroy shield generators with three mines followed by a grenade, you have to get inside the shield though. Best done with a divebombing hawk to mech mode and then jump out and throw as quick as possible.
I think some of this stuff like the early rush will get less effective once clans get out there and organized into who will do what.