With a real estate lawyer who specializes in it. I suspect that are not many lawyers who know this area of the law well. This is not something to do on your own.
I am a former federal and State prosecutor and now handle criminal defense and personal injury/civil rights cases. Feel free to check out my web site and contact me at (212) 385-8015 or via email at Eric@RothsteinLawNY.com. The above answer is for informational purposes only and not meant as legal advice.
The answer to your question may differ depending upon the State where you live and what type of government agency or utility company is exercising eminent domain. However, every exercise of eminent domain requires that the condemning authority (1) have a valid public purpose which will be served by the taking and (2) pay "just compensation" for the taking which will indemnify the owner for its loss. So "fighting" eminent domain can involve a challenge to either the government's right to utilize eminent domain OR a challenge to the compensation offered.
I would strongly recommend that you hire an experienced eminent domain attorney to assist you - there are special rules and laws that apply to eminent domain cases and it is critical that your lawyer be familiar with them in order to assure that your constitutional property rights are not violated. I would be happy to recommend one to you in your State upon your request.
The information you obtain at this site is not, nor is it intended to be, legal advice. You should consult an attorney for advice regarding your individual situation.