Go to your local family court and request the necessary forms, or locatw them online. (See Resources for a list of state court websites). These forms include the Family Law Certificate Assignment. Petitition To Establish Partental Relationship, Declaration Under Uniform Child Custody Jurisdiction And Enforcement Act, and Summons (to be served to the other parent).
Determine if your claim requires genetic testing to determine paternity, as there will be additional forms for the test.
If the recipient of your claim responds, set up a hearing immediately. Bring copies of all forms and any other documents that might be relevant to your petition. If the recipient does not respond, you have to wait 30 days to file a default form.
Prepare to go to court. Bring all paperwork and arrive early. The court may require a paternity test.
Plan ahead for possible outcomes. You will probably have to fill out a Child Support Guidelines Worksheet. The judge will work with both parties to establish a parenting plan.