The general rule for completing an I-601 or I-601A application is to document everything that you can. Following is an incomplete list of the kinds of documents that you might need. Some of them might not apply to you (you will not need a marriage certificate if you are not married, for example), and there may be some documents not listed below that you may need due to your specific circumstances. Use your common sense.
It would be unfortunate if your I-601A application were to be refused due to a simple mistake or oversight. In most cases, such a mistake will result in a significant delay in the processing of your application. In more serious cases, you could end up stuck overseas with no way to return. Following is a list of some of the most common easily avoidable mistakes that people often make when filling out the I-601A application
Certain activities can get you barred from entering the US, either indefinitely or until the ground of inadmissibility has been cured (failure to secure proper vaccinations, for instance).
US immigration law excludes certain categories of people from entering the US or, if they are already in the US, from re-entering the US once they leave. The exclusion categories are broad and sometimes vaguely defined (committing a “crime of moral turpitude”, for example, can result in a finding of inadmissibility).