Few things I would start with...first, pick the right weapon for you (plenty of meta out there) and get some upgrades on it. The right muzzle, barrel and under barrel will make a big difference. Flash hiders and silencers are highly recommended as they can hide your position from your enemies and keep you off the mini map
Second, you have to spend some time configuring your settings to match the speed and assists that work best for you. I like to mess around in the shooting range to see how quickly I can move from target to target and keep control of the weapon, and with the support of some online vids, zero in to the right settings for me. Its all personal, so I doubt someone's online tips will perfectly match what you need, but they can help explain what the settings do so you can then tweak to your liking.
Use cover and stances, and dont just run everywhere. BF is generally a slower game than some other shooters, so if you are standing out in the wide open you will get killed. Bounce from cover to cover, learn to use crouch and prone to your advantage (for example, the prone position where you are sitting down and leaning back tends to be harder to spot and can give you a split second you need to get the drop on someone. Try using the perimeter of the map to get the lay of the land and see where the enemies are, and watch your minimap for the enemy locations. If you have some good recon on the team you can get clear view of most their positions in the area, which can help you target them easier, or avoid them altogether. Also, running is loud, walking or crouching is silent, makes it easier to sneak around.
Learn the maps. A golden rule for all shooters, learn the layout of the maps and try to figure out the best paths, chokepoints, where are people likely to be hiding, going around a corner where there might be an enemy, prefire, or throw a smoke/flash to set up your entry. If something isnt working, try to go a different way. Oh, and don't always be in a rush to be the first guy in a room...as mean as it may seem, sometimes it's best to let someone else go in first and take those bullets :)
Stay with your team. Especially if you are struggling, try to stick with your team so you can support each other, and that way you arent always the 1st target the enemy sees too. Ups your chance of survival, and gives you allies that can support you with their skills and rezzes if needed.
Don't be afraid to change things up. If you keep running for a certain base, or keep using the same kit and its not working, try a different gun, or class altogether. If base A is totally camped, what other objectives can you try to take.
Try not to get frustrated. This BF is much faster than previous versions, which is why you may see all the comparisons to COD. As such, it's taking time for a lot of us to refine our play styles to the new pace of the game. And well, the hit boxes and netcode dont always work that great, so its not uncommon to think youve hit a target only to be killed yourself, or think youve made it to cover behind a wall only to be shot dead a second later. Nothing you can really do about that other than be patient and learn from it.
