Going to grad school several years after getting a bachelor's degree, during which time I graduated with an unremarkable GPA?

I’m 29 years old and exploring my career options. Grad school is one of those options, and I’m possibly considering getting a Ph.D (with the more-remote possibility of going into academia). I graduated with an English degree several years ago, with an average, unremarkable GPA, which I estimate to be around a 2.8–2.9. I also did not bother getting any letters of recommendation from any of my professors.

I blame that score on a lack of motivation, guidance and focus, as I had almost gotten the degree “by default,” since I had only a moderate interest in literature/interpretation/creative writing and couldn’t find anything that better held my interest.

So now I’m entertaining the idea of getting a Ph.D and entering academia. I’m not sure which discipline I’d like to go into, but I know that it will be in the social sciences—perhaps political science, perhaps sociology or psychology.

Like I said, I’m still in the planning stages, and any advice should be valid regardless of the field of study. So, how can I go about getting into grad school? Surely there must be other people out there who graduated with a bachelor’s a while back and didn’t grad school to be in the cards. (If there are any state-specific laws/requirements that I need to be aware of, I graduated and live in Florida).