right serious, go normal at first. I find the easiest way to get kills on normal:
automatic rifle, my personal favourite for non-hardcore is m4a1, but scar works good too
stopping power and steady aim with your choice of first blue perk (scavanger I use because of the extra nades and because with killstreaks, you can run out of ammo easy if you get a long one going)
if you have holographic scope it is the most accurate. If you use bling, use FMJ too for extra damage and impact. I wouldn't recomend silencer for normal, reduces the damage alot, even with stopping power.
Don't stop moving, and check doorway and corners, and if you know there are enemies nearby, sneak, as in crouch. Yes, you move more slowly, but you will get alot more kills and won't die as much. Always listen too for enemies moving, and remember if you die, note where you respawn, the enemy will almost always be on or near the opposite side of the map, so try to make your way over tehre to be near them and get kills. You can try to flank them or get behind too, take them unaware
It is all practice though really, you can say shoot them, but it is one thing saying it, another thing doing it, and doing it comes with practice. I'd still say CoD4 or BC2 is better though
=EDIT=
for your system running BC2, I highly doubt it. The CPU and memory would hold it back