I have been to the US Embassy many times regarding my complex family in Costa Rica. I have been extremely impressed with their professionalism and sincere interest to help.
I have also given the same advice below to numerous friends seeking tourist visas, and it has consistently worked very well for them.
1. Be completely honest on your visa application. The biggest mistake many Costa Ricans make is to try to second guess what the U.S. Embassy is looking for on their application, and they either fabricate or lie about their information. The embassy employees are highly trained professionals, and, if they catch you lying on your application for anything, even a small, seemingly insignificant item, that is an automatic visa denied.
2. Do not volunteer stories or explanations, etc. Simply answer the questions asked, briefly, honestly and matter of factly. Again, long stories given to embassy employees who have not asked for them, is a form of manipulation and, trust me, they are not going to be manipulated by any story you come up with. Such tactics again, suggest you have something to hide or are not being honest. Again, visa denied.
3. Always be polite and respectful during the brief interview with the embassy employee. Applicants who become combative, aggressive or threatening is the crudest form of manipulation and will get an instant visa denial. Although I cannot confirm this, I suspect this type of behavior gets noted in the applicant’s computer file maintained forever at the embassy and will certainly be reviewed as a negative factor the next time the applicant makes an application. So, never, never, get angry and resort to this kind of behavior during the interview.
4. Read the information on the embassy web site. Understand that the U.S. embassy operates on the assumption that you are intending to immigrate to the U.S.A. illegally using a tourist visa. The embassy employees have complete discretion to deny your visa based solely on their judgment that your complete package does not convince them that you are being honest about your intentions to visit the U.S.A. as a tourist.
What it really boils down to is simply this. When you apply for a U.S. tourist visa, you are promising you will visit as a tourist for a limited period of time and return to Costa Rica before that time period is up. Simply put, the embassy employee has to be convinced of your honesty and sincerity in making that simple promise. The embassy, rightly so, allows their employees complete discretion to make that decision based on their instincts, experience and your behavior during the interview. They are not required to give any explanation at all for denying your visa other than the obvious. They were not convinced of the sincerity and honesty of your promise.