How do I file a request to set aside a default judgement?

If you were not properly served with notice of the suit, then you would have a basis for requesting the judge to undo it's judgment.  You would file what is called a "Motion to Set Aside Default Judgment."  Some courts will call the same motion a motion for new trial or motion to vacate-- but the set aside motion is what will generally be applicable.  California has a several self-help programs.  Here is a site that has some forms you can use as a starting point: http://www.courts.ca.gov/1017.htm  .  You are not required to have an attorney, but it will help significantly if you have one to help you "make a record" to support your motion.  "Making a record" is where you put on admissible evidence as to why your motion should be granted.  If you do not present proper evidence the judge can deny your request and then the appeallate courts will also be forced to deny your motion on appeal-- for lack of proper presentment.  A well drafted motion can help you be successful much earlier in the process.  You can also visit with the clerk of the court where the judgment was entered against you.  Some clerk's offices also have forms that would be helpful in perfecting your motion.

The process starts with the filing of your motion.  The next step is to send a copy of your motion to the opposing side.  After they receive their copy, you would then need to request a hearing on your motion.  It is at this hearing that you will need to present adequate proof or explanation of why you failed to answer.  If the judge does not rule in your favor, then it would be up to the appellate courts to grant your relief.