Where can I find the best way to get First Strikes? Playlists? Gametypes?
I presume you are trying to get the first strike stance. The best way to get first strikes is to play flood. You must know where the zombies spawn and it should be easy.
Haven is the easiest to predict, the 2 zombies spawn at open ramp/Railgun/sniper at the back near the ditch.
On Solace zombies attack from opposite side to where you spawn, the usually jump off blue balcony or go around, but the clever zombies go bottom and flank the humans on solace.
On Adrift it’s best to push top mid and look for zombies passing by bottom mid otherwise you may find zombies attacking you at your initial spawn.
Complex is a little tricky to understand but you will be able to predict zombies spawn as you play.
Abandon’s zombie spawns are easy to predict also, they spawn at/around the beach area.
Play Flood, I played flood for one day and I got many first strikes which unlocked me a stance.
If you have a good connection I would suggest Grifball.
I think you can get one each round and rounds can be over pretty quickly if you’ve got a good team going for the bomb plant.
Personally, I’ve been getting a lot of first strikes playing team action sack, particularly, lightning CTF and fiesta but only fiesta when I spawn with a good power weapon:
Play Flood it’s the easiest and you have the potential to gain three First Strike medals. The same can also be said for Grifball.
Word of caution on Grifball - If you don’t get Pro, it’s only one first strike for the game. And majority of people seem to prefer “Infinity” Grifball over pro. 
I got a lot of first strikes and thus my first strike stance (which i Don’t give a s**t about really, but some kids obviously does) by playing Btb on exile and at spawn running to middle bridge at start.
Spawning blue side, going on the left side towards the middle bridge you can sometimes get aim on AFK-players…this way i have lots of easy kills!
SWAT on Haven or Flood on Complex.
Flood is your best bet. Every round gives you a chance to earn a first strike medal.
Oh man…Snickers and Blues beat me to it. Op, like they said, Grifball is your best chance of getting First Strike. You can get it 3 times, if you’re lucky in Grifball Pro.
EDIT: Fixed “Griffball” to “Grifball”
> Oh man…Snickers and Blues beat me to it. Op, like they said, Girffball is your best chance of getting First Strike. You can get it 3 times, if you’re lucky in Griffball Pro.
Just one F in Grif BTW. (Yes, it matters that much.)
Anyways, if you’re playing alone, I would suggest Flood because you have a better chance. If you’re playing with a few people, then play Grifball and choose Pro. Be sure that your teammates don’t rush in and steal your First Strikes, though!
> > Oh man…Snickers and Blues beat me to it. Op, like they said, Girffball is your best chance of getting First Strike. You can get it 3 times, if you’re lucky in Griffball Pro.
>
> <mark>Just one F in Grif BTW. (Yes, it matters that much.)</mark>
>
> Anyways, if you’re playing alone, I would suggest Flood because you have a better chance. If you’re playing with a few people, then play Grifball and choose Pro. Be sure that your teammates don’t rush in and steal your First Strikes, though!
Wow, I must having a major typo problem today. 
OP, like Sensor said, once you start Grifball Pro, you gotta “haul some” if you are gonna make the First Strike, lol.