If there was an active warrant for someone, how would that person find out?

Given the very few facts you list, the answer is NO. If you believe that you are charged with a crime, and a warrant has been issued, either contact the court/law enforcement agency you believe holds the warrant to confirm the warrant; or, consult with a lawyer admitted to the practice law in that jurisdiction and the lawyer can contact the court, etc, to confirm the warrant. Good luck.

DISCLAIMER
Since I do not practice law in your State, this answer is provided solely for informational purposes only, for you to use as a starting point when speaking directly with a lawyer in your State. This answer does not constitute legal advice, create an attorney-client relationship, or constitute attorney advertising. I urge you to immediately contact an experienced criminal defense lawyer admitted to practice law in your State before you make any decisions about this case.

With a warrant, most police department and counties share their active warrant information with the public. Many times, they know that citizens will take care of the warrants if they have a way of finding out about them (thus saving the municipalities a lot of money for executing the warrants).

The problem is you have to know what law enforcement agency has issued the warrant because they typically will only give the public info about their own warrants. So for police department and municipal court warrants, call the local police department. For JP, Court-related, probation, and Sheriff warrants, call the sheriff's office.

A lawyer should be able to help you find who has issued a warrant and help you do what is called a walk-through to get the warrant withdrawn and your case set in court. Talk to a local criminal defense attorney ASAP.

Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.

I would also suggest contacting the Harris County Sheriff's Department. They should be able to tell you if there is an outstanding warrant for you in Harris County.

A bonding company may be able to help you as well.