This is my first Iron Banner, and it is driving me NUTS how many people suck at playing Control. It's mostly Bungie's fault, because the goddamn game practically begs you to play it incorrectly.
Control is a standard "Deathmatch mode", with bonuses applied to holding one ore more "control" points on the map. What many people don't realize is that you don't get much in the way of score by holding these. What you get points for is killing Guardians. You get more points the more control points you hold.
That's simple enough, but the problem is most maps are asymmetrical, and it's easier to hold one pair of control points than the other. In general, when you hold point A or C, you and your team are going to spawn there. If A or C is closer to B, that makes that point more valuable to hold.
What happens is you'll be holding A and B, and racking up score, and then one of your misguided teammates captures point C. That's good, right? I mean Lord Shaxx just said, "YOU CONTROL ALL POINTS! TOTAL DOMINATION!!!" You and Lord Shaxx are both wrong. Now, since he or she just captured point C, that becomes a valid spawn point for your team, AND his presence there prevents the opposition from spawning there. Congratulations, you just "flipped spawns", and are probably going to lose both A and B, and since A is closer to B, it's going to be much harder to retake either point.
Now, if you see this happening, (basically when you see one of your dumbass team members begin capturing a third control point), you can prevent the swap, by basically crashing the point you want to hold and sweeping through the spawn points. Usually, you'll have to kill a guardian or two, then said dumbass will move on, no longer blocking the enemy spawn, and the points will flip back. Conversely, if you've been dominated on an unbalanced map, be sure to take advantage of the other teams dumbasses who try to capture the third point. While they're doing that, crash the point you want, it will flip, and soon you'll have "B" and ready to rally.
Here are the standard maps with my opinion on which two points are ideal. My standard for ideal is they are close together, with good lines of sight to all approaches to both sites.Twilight Gap - A / B - This is actually a fairly even map, some might prefer to hold B / C. If your team is holding that, I'd suggest playing along, because it's not worth the slight tactical advantage at the risk of a spawn swap.
Rusted Lands - B / C - This is fairly even too, but I think there is a decisive advantage to B / C. I'd only risk the spawn flip of my teammates are hopeless.
Firebase Delphi - A / B - This is a very imbalanced map. It is absolutely critical to hold A / B. IN fact, if I spawn at C to start, I'll often crash A just to see if I can kick off the spawn swap early. It often takes people off guard, I can get a first blood, and swipe the spawn while most of their team has moved on to B.
Blind Watch - B / C - Another very uneven map, same strategy applies, take B / C at all costs.
The rest are somewhere in between balanced and unbalanced, so it's almost always going to be worth it to hold these points.
Shores of Time - B / C
Asylum - A / B
The Burning Shrine - A / B
Exodus Blue - B / C
The Anomaly - B / C
If you're experience says otherwise, I'd love to hear it. Especially for Twilight Gap or Rusted Lands, as my preference is pretty slight.
The only exception is if you are just completely dominating a completely helpless team. Go ahead and cap all 3, it will hasten their defeat and be an act of mercy. But I'd only do that if you're double their score mid-way through the game.