What I have seen is 2 strategies.
One, and the most successful, has been the all out blitz with man to man coverage. We have typically put good pressure and forced the QB into making a tough play. Sometimes it happens, sometimes it does not.
The 2nd is a zone defense where we get 3 linebackers and at least 1 corner spread out just a yard or so in front of the 1st down line. In my opinion, this is the defense that is killing us. I have seen countless throws in front of our linebacker who makes the tackle only to have the receiver stretch out as he goes down an gets the 1st down. Happened 5 times against Penn State. A few times, we played the linebackers up 3 yards off, only to have a safeties stay back!! That left a huge gap which Penn State exploited with crossing routes.
The blitz strategy can stay in the book. But the zone strategy has to change. We need to move the linebacker up to 3 yds from the 1st down marker and move the safeties up too. Yeah, we might get beat deep once and a while. But I will take that over the 50%+ 3rd down conversion rate we currently have.