If you're a complete beginner, hopefully these tips will help you on your way.
Let me start by saying up front, it's perfectly OK to be a beginner. Everyone has to start somewhere, regardless of what the internet may have you believe. What Call of Duty: Black Ops 3 is a fast moving experience with a bunch of weapons and maps to master, with the added challenge of going into combat against players that might have vastly more experience.
I came in to Black Ops 3 completely fresh, without much experience of previous CoD multiplayer games. If you're the same or thinking of jumping in, here are some handy tips that helped me suck a bit less. They should be good for Xbox One, PS4 and even somewhat for PC.
The very first thing you should consider is your controller sensitivity. If it's not right for you then your aim will be all over the place. A lot of people think it needs to be super sensitive so you can flip around quickly and get people coming in from behind.
Newsflash: If they're behind you you're probably already done for. Think about what you can see, and if your sensitivity is up to 12 you'll be twitching all over the place and struggle to control your recoil.
Pro players will often turn the sensitivity right down, and so should you. See what you're set to start with, and then play a couple of rounds at one or two above and the same below. Try out the different settings to find where you feel most comfortable. For example, mine started out on 5, I turned it down to 4 and that's what's working best for me.
Once you're happy with your sensitivity settings, the other thing to do to work on your aim is to practice. Black Ops 3 moves incredibly fast, and a moment's hesitation on your aim will turn what would have been a kill into your own death.
Of course, jumping into Free-for-all or Team Deathmatch frequently are great practice. But if you want to sharpen up without worrying about getting pegged by a sniper, set up an empty custom game. Do this by starting a custom game in multiplayer and not allowing anyone else to join.
For example, an empty Nuketown has a bunch of things for you to practice aiming on. There are mannequins dotted around the map along with plenty of points on walls for you to target. Run around and try to hit things precisely. Practice makes perfect.
Focus on what you can see, not your stats
It's really easy to get carried away and super frustrated at your Kill/Death ratio. But guess what? You're going to get killed. A lot.
Instead of worrying about your stats, focus on just playing the best game you can. The stats will improve as your ability does, there's no reason to force it.
And if you find your numbers have dropped significantly from the start of a session, take a break. Grinding on when you're clearly getting frustrated or fatigued won't help, and you'll just get into more frustration and rage. Know when to set aside the controller before you rage quit.
Wall run, jump and slide all the places
While critics of Black Ops 3 will lament all the boost jumping, power sliding and wall running, in a multiplayer setting these are important skills to master.
To reduce your death tally you need to be as difficult to hit as possible. Sliding through doors is a great one to try. Don't just run through it and leave an easy target to hit. Slide through and then maybe tag a big ol' jump on the end.
If you're flying through the air or tearing along a wall you're more difficult to hit than if you're just running along the ground. Which gives you an advantage over the person on the ground trying to get you.
Tweak your controller layout
There are a number of different controller layouts available inside the game that might benefit your style of play.
One that's worked well for me as I get to grips with Black Ops 3 is the "Stick and Move" layout. This essentially swaps the function of the right stick and the 'A' button.
'A' becomes melee and pushing the right stick becomes jump. The logic here is that you're using the right stick constantly to aim, so using it to jump means you're not moving your thumb to another button to jump, then back to the stick to aim. It might help you react better while you're moving through the air since you're not moving between buttons.
So, that's five key things that I picked up while looking for tips that have really made a difference to how I approach the game. Even after a short time I'm already enjoying it a lot more. If you've got any tips of your own be sure to share them in the comments below!