To my view point ,GRE physics can be improved significantly if one solve a lot of problems while preparation and does not waste time doing one problem only.
I improved my score on GRE pyhsics by buying the following problems.
Physics by Hliday/Resnick/Krane.
Physics by Gettys.
Gold resources notes.
The most important factor that improved my score that i bought all manuals also.I didnt stop on one problem if i failed to solve it.
I tried mt best to solve each problem but when i observed that i cant solve it,i opened my solution manuals to solve it.In this i solved a lot of problems in minimun time.
Another advantage of using manuals is that one become familiar with a lot of approaches to one problem.The problems on face in real GRE are similar to these problems.
Above metiones books one ccan buy from amazon.com(http://www.amazon.com)
and manual can be bouht from goldresources (studyresources@yahoo.co.in)
studyresources also has a website but i dont remeber its name.Google it if you are interested.