How to prepare for STEM graduate program while in industry? I recently graduated with my bachelor's in Electrical Engineering and started working in industry. During my undergraduate work, I had always planned on going back to school, but it wasn't until shortly before graduating that I realized that I really wanted to pursue academia and become a professor. I only applied for the graduate program at my own school during senior year, since I didn't have connections anywhere else at the time. I wasn't accepted, but I recognize now that I'm not quite ready for grad school.

Now that I'm in industry, I've been working on goals to help prepare me for grad school in 3-5 years from now. I've been going over my old math courses to crack down on the basics, reading academic journals in my area of interest, and using my remaining free time to study and work on projects in areas that will make me more knowledgeable.

This is something I’m really driven to reach, and willing to put in the hours to accomplish. What other things can I be doing in this time before reapplication to better prepare me and make me a more competitive candidate for grad school? (Besides the obvious, like a good GRE score)
If you haven't, reach out to your adviser and/or other professors at your undergraduate university for two questions. Can they give you any insights into why your application was unsuccessful? Do they have any suggestions? The second question could be expanded into--do they feel you have any particular weaknesses or strengths? What universities do they think would be a good fit for you? 

Possibly taking programming/computer science classes might be useful. If there's a university close by, see if you can take a grad-level or senior-level ME course as a non-matriculating student. If you plan to apply there, make sure that it won't adversely affect your curriculum if you end up going there.