How can i stop dieing in battlefield bad company 2?

ive been playing battlefield bad company 2 for a while and i never get a kill im always dying and wich class could i use to get kills? oh and once i finish getting all weapons and gadgets for a specific class can i keep using it but can the points used for that class go to another class or does it just add up to your rank? please helpHow can i stop dieing in battlefield bad company 2?
In really depends on your gaming style, always join a squad, if you are in one and spawn on them when they are on the front lines, spawn back at the starting area! Normally use Recon and pick off enemies :) if your assault your job is to be a all round soldier :P! this means you will die.