I receive many requests to find arrest warrants. Unfortunately arrest warrant information in California is not public record to a 3rd party- except for San Diego County - Thanks to Paul Bush of Legal Dockets online for reminding me.
In some other states, warrant information is available online. Check this link of a City in Kansas - City of Rose Hill Warrant List
Another way to check for warrants is to run a criminal index for the individual. If there is a pending criminal case, contact the court to see if there is a "Failure to Appear." Most likely if there is an FTA, then there is a warrant. Also, run the individuals driving record. FTA's show up for traffic violations if the Subject does not show for his traffic court case. Law enforcement will only pick up that person if they are stopped for a traffic violation.
One other way to check warrant information is to check the County's most wanted list. Granted not everyone will be on that list, but some small counties will list everyone with a warrant. Try this link - Most Wanted Persons by State