Unfortunately, the military experience in the Far East has clouded the issue. The US is one of the most restrictive countries (unless you are rich). Worse in the last few years as more restrictive legislation has been passed. When you marry an alien you lose much of your rights too. So a lawyer is a must. Although you can do it by yourself I cannot recommend it .
First, you need to aquaintance yourself with the customs and mores of the country your prospective spouse comes from as there are vast differences in attitude,traditions,customs,and financial views. Many countries have no safety net of social services. The social class that he or she comes from may render them unable to quickly adapt to life in the US and they may not have the life skills that we take for granted.
I strongly advise research into the “supposed to be’s” of the expectations and to sit down and really approach this from a business stand point whic is of course alien to most Americans. Many societies have “arraigned marriages” and the family is part and parcel of the marriage unlike the nuclear family of the US. Extended families and responsibilities and obligations may not have been voiced as assumptions abound.
Language is a real barrier. This is because translation softwear cannot deduce nuances of speach and may miss an important change.
Non-latin based languages are far more difficult because there is no common ground.
Because of these factors 90 days is far too short a time as it fall within the “infatuation Zone” and the real person may not reveal themselves nor you because of the newness of the relationship.
You should be very aware of what their culture and social class puts forth as proper behavior!
A custom in the US may be seen as insulting and demeaning to a person from another culture.
For a real glimpse: babel fish does an ok job of translation, but misses nuances and in spoken word many languages are Tonal: American English is for the most part is not.