I live in Texas but have a warrant in California from 20 years ago that I'm trying to get resolved. I don't know where to start. What are the steps to take?

I'm licensed only in Texas, so I can't advise on California procedure, but here is the general picture. An old California warrant does not expire just because time has passed. It can show up in a background check or a traffic stop, and a person can be arrested on it, including in another state. Whether California will come and get someone from Texas depends on the type of charge and the county, and that is not safe to guess at.

Most people start by finding out exactly what is pending. The clerk of the California court where the case was filed can confirm whether a warrant exists and what the charge is. A California criminal defense lawyer can often ask the court to recall the warrant, and in some cases appear for the person without them traveling. California's rules on drug possession have changed over the years, which may affect an older case.

Hiring a California-licensed lawyer first, before contacting the court yourself, is generally the safer way to handle this.

contact a criminal lawyer in CA and get them to help.  I just had this for a client.  you need CA counsel to lift the warrant.