As a caveat, I'm assuming you have a basic knowledge of how to play the game in terms of controls. I don't really want to go through a list of controls for all three platforms, so provided you have prior knowledge of how the basic mechanics of the game work (and you know how to join a game too) we can begin:
- Picking the right class. Selecting the best class to use in the situation is the first aspect of Battlefield 3 multiplayer that you simply must get right. Sure, you can have fun as any class, but my Battlefield 3 multiplayer manual is all about winning- and having fun in the process. The first step to knowing what class to pick is to look at the map. If you are playing on a more enclosed map then you should be looking at Assault, or possibly even Engineer for shotgun capabilities. Support is alright, but spray and pray is no match for a close range assault player with good accuracy. On the other hand, a map with lots of wide open spaces and sniping zones means Recon comes into its own. Next, you need to look at the mission objectives to determine which class to spawn as. Lots of blunt assaulting of chokepoints is going to warrant Support or Assault. If it is a vehicle heavy map Engineer can be useful here too to take down enemy vehicles.
- Working as a team. One of the hardest things to do in Battlefield 3 is to work effectively in a team unit. Because your team is liable to change every single time you play the match, and because you could be playing with people thousands of miles away, building up a good sense of team strategy is rather tricky. However, there are a few little tricks you can employ to build up your teamwork in BF3. Firstly, make good use of the text chat function (this is for PC players) you can type up quick orders on the fly and then pass them on to the rest of your team. You can also report on enemy movements etc much more easily this way than by headset communication. Usually headset communication in video games just turns into a farce very quickly- but if you are assertive and confident on the mic you can often wind up leading your team more effectively.
- Focus on the objective. I have said it before and I will definitely say it again- focusing on the objective is the best way of winning in BF3. If only the Battlefield 3 manual reasserted this important tenet of multiplayer success enough. Of course it's fun to try and fly an attack helicopter through a tunnel, but if you want to win (which is why I assume you are reading this blog) then you need to focus on the objective. Not only that, but you need to get your team to focus on the objective too. Use clear communication and get people to work towards the objective- this way you will win and have a lot of fun too.