First time I went to the track it was in 2500 DA air, I was launching at too low an RPM and wasn't careful enough about shallow staging. I also made no attempt to limit heat soak. I was also in the low 13s.
Since that time, I have gotten better at launching - now I just barely let the 2nd staging light come on and I bring the RPM up to 2000. Before going to the track, I remove the engine cover and weatherstripping at the back of the hood. When I get slowed down at the end of a run, I pull the hood release and let outside air flow through the engine compartment as I am driving back to the pits or staging area. Since that first time, I have not been out of the 12s and the runs are amazingly consistent.
As for tire pressure, I cannot argue with SHOnuUp since his times are awesome and he lowers his tire pressure. However, for my car and the tires I run, I have not found lowering pressure to be a benefit. What it might help in the 60 seems to hurt with more rolling resistance as the speed builds. Again, this might just be due to the tires I run - 18 inch Goodyear Comfortred Touring.
The point is that a few little tricks and some practice makes a big difference.