Lol, what i do, is play wired to router, since my pc is freaking far from the modem >.>.
get game booster like everyone above said and Ccleaner to clean out all the shit in your pc

then play at your preferred resolution, but at 16bit ( cant tell the difference between 16 bit and 32 bit, in terms of quality)
play at all LOW settings with 100 sound effects and mininum music volume on.( blood is useless, even though my account is 18 xD)
btw, CLOSE ALL USELESS PROCESSES, a little can add up to a lot
with this, i lag around 1 time every 5-10 games(sometimes never in a day)? cuz my lil sis plays sims on her pc and goes on aim, lags the shit out of my pc when i surf the web( not for porn)
ALSO, if possible, get CABLE internet, not high speed. high speed can suck my balls

although i really want the T1-T3 internets.. cost like fuck though