How to prepare before going to grad school
Prepare financially. Grad school is not cheap. Make sure you can afford it. Even if you're going to be funded, you're probably not going to be well-paid, so the money you can save now, while you still have a job, will be precious. By having a reserve available, you can mishaps like this one since even if funding runs out you'll be able to self-fund.

Prepare a fallback plan. This ties in with #1. Do your current job well. If you manage this, then if you go to grad school and find you dislike it (happens quite a bit, e.g. see this question) you can still hopefully return to the workforce seamlessly. Perhaps you can rejoin your original employer, perhaps you can join a competitor; either way you have a lot to gain by achieving a lot in your current job. Your employer might even be willing to fund you through grad school.

Start worrying about how to find a position. After having done the two things above, start thinking about where you're going to study. Which universities are you going to apply to? Which professors do you want to work under? What topics do you want to learn? Do you want to take courses or do you want a research-only Masters? Here's where money can come in handy again, because if you're able to self-fund you'll have a wider pool of potential universities to look at.

After you've identified a university/professor, the next thing to do would be to write to read some of that professor's papers, write to that professor to make contact, possibly discuss some aspects of the intended work, and apply. If you are accepted, then you can ask the professor about what to study before attending.