You're then left with making the choice of which base to target. Travel behind enemy lines and inspect the bases, their general number of soldiers, their special resources (radio towers, anti-air emplacements, cargo trucks, prison transports, etc). You might notice that the bases without any specialties farther away from the border are actually pretty weakly defended, which offers you a great opportunity for a side base capture. You probably already have a few squad members by the time you get to Moorland Trenches, making capturing bases with a squad easier than without. Chances are you also have radio available by now, so you can also request paratrooper backup at the base you're storming yourself.

Paratrooper backup may be denied by the enemy anti-air emplacement somewhere in the map, so make that as your first mission. Again, scout the map, find the location, and call in mortar strikes on it or if you can handle it, use C4. Always good to bring silenced weapons for these missions, and wait for night before you go in for the task itself. If you get caught, back away and let things cool down a bit, and try again.

Now as you go behind enemy lines, you'll risk by playing far from your territory spawn points, meaning if you die, you'll have a long way to go there again. Consider using the Spawn truck as a restore point (or flares even if you have the rank and RP), you can at least spawn somewhere a bit closer. Just make sure the truck doesn't get too close to combat zone or the spawn point becomes disabled. If it does and you lose it, then there's your new mission, get the truck back from the enemies.

Stashes work behind enemy lines as well, so it may be useful to stack some goodies there in order to gain access to them while you're away from armories and if you die and lose some of the special items. C4, vests, sandbags, prepare and keep some extra in the stash.

So yeah, anti-air emplacement sabotage, side base captures, what else? You'll stumble on radio towers here and there. They may be well guarded, but it's nowhere impossible to be able to get inside and place a C4 on it. Blowing one up will stun the enemy faction comms for 3 minutes, stopping their soldier spawning and their soldier transports between bases -> chances are you or your faction's main attack party can use this period to capture the next base and reinforce it properly. You may also fluke out and find your faction's main attack party having captured an enemy base which had the tower: destroy it.