For those without unlimited power, here is how I would play:
There are SO many portals now, and many of them are unclaimed. Try to make it a point to take over 1 portal per day, either by force, or finding an unclaimed one.
Destroy portals -randomly- it feels great and they don't see it coming. Even if you only put L1 resonators in it's place, you gained at least 2350 AP from the venture. Level 4 agents can destroy a level 6 or even 7 with a little determination. More links = More AP = Leveling up faster
Small weapons can make a big boom if used properly! L1-5 XMPs are best used directly on top of the resonators. If the portal isn't at full power, SMASH IT! Remember, portals drop their links if there is only 2 resonators left. If you can't destroy it, cripple it. This is where you will gain a ton of AP.