First of all just play until you know the maps, don't worry about your K/D just learn the maps, follow a couple of high level players around to see what they do, learn all the nooks and crannies of the maps best areas for capping flags, best short cuts to the next objectives.
If you run like Leeroy Jenkins everywhere you'll get nowhere you really have to be careful.
There are the four different classes as you know each of the weapons are different even under the same class so get yourself on Battlelog
to have a look at the guns for each class, some have a high RoF but higher recoil and others lower with less recoil there are other aspects but these are the main one you'll want to consider.
As you play with each class you'll unlock new guns and gadgets as you play with certain guns the more kills you get the more attachments you'll unlock like scopes and suppressors as you level up however you'll unlock PDWs and shotguns that can be used on any of the classes unlike say snipers which are recon only.
Then there are vehicles, as you earn points in a vehicle you'll unlock new perks for that vehicle you'll want to try everything out because it can be fun but watch out for anti-tank mines, C4, or anti-tank soldiers if your in an MBT or IVF. If you are in the air well it takes a lot of practise, try the basics first in the comfort of your base if you can and then fly out and try to take some people on be warned you'll get your ass handed to you in the air.
Check this out on a guide for jets -
And this for a guide for choppers -
I'm leaving out the basics because you can really pick up the basic flying pretty easy but things like killing lock can be really difficult which is where the videos help when it comes to one-on-ones.
Little things like firing off one heat-seeker to draw out an enemy pilots flairs and then firing another to score a hit is a nifty trick instead of firing both your rockets off as soon as you have lock but you'll pick it up as you get a hand for the game.
Soon you'll learn more advanced tricks like hitting the buildings in Bazaar with an RPG to knock rubble down onto the enemy to kill them, but for now just play to get a feel for the game it'll take you 20 hours until you're 100% with all the maps, remember don't stick to one map play them all.
Good luck, and remember you can always join the PS3T Battlefield Clan
. [/shameless plug]
*Edit - Remember to always spot your enemies with the Select button. It helps everybody.