Though walls don't count, if you have a moment to spare, ink walls that provide access to higher ground. Just do it in a manner where you are not wasting too much time on such side tasks. Even if you don't intend to go up immediately, your teammates would appreciate the newly available path. Also, you want to keep as many possibilities as possible open, cause you never know when you or your teammates may need to make a desperate escape from danger.
For chargers, don't charge every shot. Rapid-fire to quickly ink tight areas, while squiding forward often to replenish your ink. Keep your eye peeled for opportunities to blast a long strip. Positioning is key, especially for large open areas where you generally want to find a rhythm; charge, blast, sidestep...charge blast side step.
Remember to utilise your sub weapons and specials, especially once you get access to sprinklers*, and ink strike*. Those two will greatly aid chargers in turf war.