Preparation of the I-129F visa application
First you and your fiance need to assemble all the information that establishes your relationship. This includes, email correspondence, love letters, phone records, and plane tickets of trips to see each other. Photos of both of you in different locations are very helpful.
Interview at the US Consulate abroad
After the I-129F petition has been submitted to USCIS and approved, then the fiance will have an interview at the US consulate abroad. The consular officers may ask questions about the relationship and other evidence provided.