I'm currently interested in pursuing a graduate degree in computer science, but right now I am working full time and will need to continue to do so for a few more years until I can pay off my undergraduate debt. I also have very limited research experience as an undergraduate. That said I was wondering what are some small things I could incorporate into my daily routine to both prepare myself for graduate school (I've noticed the work in the corporate world is very different than school) and make myself a more attractive candidate when I am able to apply?
To prepare yourself and keep your skills in shape, one idea is to gradually go through advanced undergrad/beginning graduate textbooks, including doing exercises. (Reading is good, but also doing exercises (both theoretical and programming) is better.) It might also be good to do a programming project or two, from which ideas might naturally stem out of your reading. What to go through also depends on your situation (what area of CS, what you learned already, whether you're already programming for work...)
However, to make yourself a good candidate for graduate studies, you'll also want good letters of recommendation, which means you want someone (ideally an academic) familiar with your further preparations. Therefore you might try contacting one of your old professors or a professor geographically close to you to see if they're willing to help give you some guidance in your studies and/or involve you in a research project.
I took a year after my undergraduate degree before applying for my PhD studies. In my experience of discussing this break in interviews, the best thing to show is that you were still interested in the subject and have kept up to date with what is happening. I joined the Institute of Physics and regularly read their members magazine, which kept me up to date with the latest research, trends in funding, and new technology and methodology. Mentioning recent discoveries or being able to give an opinion on current debates shows your dedication to the subject, interest beyond your own work and often helps provoke conversation with your interviewers which makes everything a lot more relaxed.
In summary, I would recommend subscribing to relevant research journals or magazines, or possibly finding blogs of researchers you admire, to keep your knowledge of your subject up to date.