If you haven't done so already, it might be worth focussing on some specific topics which always show up on the PGRE.
For example, you should read the first chapter of Griffith's book on Particle Physics thoroughly. You'd nearly always get a couple of really simple questions from that chapter.
For special relativity, I think there are only 3 kinds of questions which can be asked. Just practice each type well and you'd be able to crack them with your eyes closed.
For mechanics, it's useful to keep some standard formulae at hand like for example, the energy transferred in an elastic and inelastic collision, rocket equation etc...
For electrodynamics, boundary conditions are extremely important and you might be asked some tricky questions on calculating the electric or magnetic field after a reflection.
Last but not the least, it might also be useful to do a bit of general reading on the latest stuff happening in physics, particularly the nobel prizes. There are always some random questions on them.
I hope this helps!