cool , yea i am a big time 3-4 user , and i have been messing with some of the books that have both 34 and 43 (Jet/boys/raider),
theres a couple of main ways that i use th3 34 depending on my players , my mood, the team i go against and all those factors...
some people use a rusher every time , called the rushEnd Linebacker , he is usually the Outside linebacer on your defense's right side. IF i do this , I make sure to put in a pass rushing beast at that position if possible , and i will cause havoc with him most of the time. That D is like the 4-3 except your guy (the rush end) isn't a cheeser if he moves around or even drops back even tho he usually rushes..
or if you go to more of a flexiblle amoeba like balanced 3-4 - where the 4 linebackers are more balanced , you probably want to put in some LBs that can cover and maybe even a safety/linebacker hybrid (for example troy polamalu) as the 4th linebacker, you can call more man-to-man with this and the blitz is a little less predictable , altho less concentrated.
Real 3-4s take advantage of occasionally blitzing safetys or even corners , they are always talking about "blitz packages" when talking about a 3-4 defense coach...