This is California we’re talking about, so first conduct a Business Entity Search through the Secretary of State (use both of the primary categories). Then if you think there could be trademark issues, use the TESS System through the U.S. Patent office to check. We recommend searching both databases to be prudent.
Now, in California each county has a different Fictitious Name Statement form. So, head to the California’s Counties page through the CSAC and contact the one where you intend to set up shop.
Once you get your hands on the form, digital/hard copy (if you don’t have legal representation and you aren’t working with a DBA filing service) read and understand every word.
Once you’ve double and triple checked after filling out the form, have it notarized and then file with the right county. The fees are different but you’ll know right away once you contact them (or it’ll be on the form itself).
Within your first month of filing, you’ll then need to publish your Fictitious Name Statement in a local newspaper. This should be done every week for the next four weeks. They’re all quite used to it.
After that time, you’ll need to give a signed Affidavit of Publication to the county clerk. This should also be done within 30 days of the last date of publication. After that you’re good to go!
This guide is for information purposes, not a legal document of any kind. Furthermore, the specific details tend to change over time depending on your area. Please consult a business lawyer for specific legalities and details on filing a California DBA or specifics on starting a business.