I'm horrible with spawns, it's definitely the worst part of my game. I often don't even pay attention between waves, I usually just focus on going to ammo boxes or taking out Turrets or Swarmers. Yes, I'm a spawn-ruining PUG.
The one map I seem to get the most "spawn-fighting" about is Jade. I prefer to sit to the left of the LZ, suppressing the spawn in the back hallway and making the spawn come up the stairs at the end of the hallway. It gives the team good sightlines and RHA for all the enemies. However, a lot of players like to go to the little platform down the stairs at the end of the hallway and make the enemies spawn on the opposite side of the map (esp. the control room on the opposite side). This is stupid, because if somebody doesn't sit in the back hallway, the enemies will respawn there and you'll be flanked without a lot of cover. So what usually happens is that I'll sit in the hallway and suppress that spawn so they don't get flanked for a couple of waves, then I'll get fed up and abandon my post, which gets the other people killed.