It's difficult to say because schools weigh various credentials somewhat differently. Though, most schools will probably filter out potential students on the basis of their GPA and GRE subject test scores more than anything else.
A GPA of 3.5 is solid, though you should try to boost your GRE physics subject score if possible. A GRE physics score in the 20-25th percentile isn't very competitive, even for average schools. Though that's not to say you won't get into some of them.
I wouldn't be overly concerned with your GRE general score unless you're planning to apply to top-tier schools (in which case, you'd also have to do much better on the subject test). Otherwise, I'd say a verbal score of 500+ and a math score of 600+ would do for most average grad schools. It is still worth studying somewhat for the GRE general test because I know some people who did tremendously well on the SAT, but bombed the GRE general.
Also, I would agree with invidia that undergrad research is very important to grad school admission committees. Perhaps it's a bit late now, but if you can still find time to schedule some research, it will certainly help quite a bit. It will also give you an opportunity to get letters of recommendation that outline your research potential.
In addition, most students underestimate the power of a very convincing and well-written personal statement. I know some people with sub par credentials who were accepted into some pretty competitive schools on the basis of the determination they expressed in their personal statement. You want to be specific and sound excited, aggressive, challenged, and very motivated in your statement.
Overall, you have a decent GPA. If possible, try to boost your GRE subject test to at least the 50th percentile and be well-prepared for the GRE general. Getting some undergrad or post-undergrad research, if possible, will also definitely be to your advantage.
Hope this helps. =)