All of the relevant application forms for my wife's I-130 are in the consulate office in Guangzhou. Before I answer more questions I would like to encourage visitors to at least consult with an immigration attorney. Minor mistakes, which are often avoidable, cause major harm in immigration matters. It seems so simple, but remember that you are dealing with important legal issues. Attorneys can assist you so that you attend the interview and are fully prepared at the interview.
Attorneys can also assist with procedure, making sure the case is on track.
The law does not require you to have an attorney, but many people feel it is useful. If you go to the interview with even a single item of evidence missing you will cause a delay. If you can live with that kind of delay, no big deal. Teachers are a good example. The bottom line is you will need to convince the consulate that you can afford to live in the US with the legal salary you will be earning.