USA, Canada /
Info about USA VISA. Applying for a US visa, in Warsaw [4]
I'd assume you are applying for a tourist visa?
Tourist visa is one of the hardest to get. You have to have proof that you are actually going there for enjoyment and not trying to immigrate illegally or for work. You are basically guilty until proven innocent.
I'm not familiar with Warsaw, but my girlfriend at the time was applying for a tourist visa in Krakow.
What you need is specific travel plans to be the most convincing. They also take into account your age, your personal ties to Poland, and your financial standing. If you are young, poor, and have no reason to stay in Poland, you will defiantly be denied a visa.
However, if you show that you are just looking for a vacation and some sight-seeing, they will be happy to give you a visa. My ex-girlfriend was a student, so she had definite reason to return to Poland. She was issued visa that won't expire for 10 years.
She's still coming to visit me this summer, but the distance was too hard on our relationship =/
Other things:
you have to apply for your visa online which is then submitted to the US consular in that particular city. Then you will have to make an appointment to go meet with them. You have to pay for this ahead of time and I'm pretty sure it costs about 300 zl. Speaking english if you do so fluently is a very good idea when you meet with the person. It could take anywhere from a few weeks to a few months to get an appointment, so make sure and schedule plenty ahead of time.