Part of the challenge is that, no matter what you do, some readers will bring their own biases to it. What does that mean? It means that readers will seek the familiar, and that includes trying to slap on some serial numbers on things that you didn't even scrub them off of. What does this mean? It means your readers will sometimes find parallels to real-world cultures that you never intended.
And then ping you for doing it wrong.
Can this be avoided completely? No, of course not. But there's things you can do to minimize it.
- Don't make your racial distinctions stereotypical or offensive. Make your secondary words racially diverse, but try to be aware of how you depict that. I've found Writing With Color to be a great resource to help with that.
- Learn where your culture is coming from, from the ground up. I'm not saying you have to build it entirely from the bottom. But if you understand some underlying basics-- what they grow, how they use that, what they eat, what they build-- that gives you the tools to guide them in their own unique way.
- Steer their language away from the obvious. If you're looking at your new culture and think to yourself, "this sounds like Eastern Europe", consider making the language base (and thus how you name places and people) something that is nothing like Eastern Europe. Vulgar is a great resource for that.