Secure a knowledgeable international law attorney. Do a search online to find the best international lawyers in your price range and to best suit your case.
Compile any and all information you've collected that will be beneficial to your case. Keep explicit notes and recall every detail of the incident before filing suit. It is best if your notekeeping is done during the events; however, compile them even if they are written later, since it will help your counsel.
Make an appointment to visit with your attorney to discus the future of the case and the strength of your case. Be realistic about your prospects of winning and the costs associated with pursuing your international suit.
Do some research on cases similar to yours or the success of cases filed against the nation you are filing suit against. Be proactive in learning about the law along with your attorney so you can stay informed on the process and the limitations of the law internationally.
Gather any other parties that may be involved with your suit to help give it momentum and validity. Determine if the size of your case is large enough to employ a team of lawyers to work for you or your party's behalf, since it will expedite the process.