Try shiffting your line around to one side and overload a side! Also if you have a speed rushing DT with strength right off the snap tap x and he can usually just push the Oline over and get the QB. If your a DE then shif the line overload the side and then spin or cut to get the QB..
I play online a lot and usually get a lot of sacks each game... Another technique that works if you shift the line say to the left then blitz with the OLB from that side normally they wont even block you!
You really shouldn't even play as DE or DT, you can be much more effective as a MLB if they're run oriented or a safety if they're pass oriented. If they're just throwing long bombs to Randy Moss or somebody just play the CB that's on that WR, that is, if you're good, CB is VERY VERY hard to play.
I use Elvis Dumervil who is average but he's quick so I fake too try to run by, then cut back inside and it works REALLY well after a while doing it you get a good feel and eventaully master it where you do it automatically.