That person will be seeking, most likely, what the US calls a B-1 visa. This is a visa that allows a person a visit to the United States for business purposes (http://uscis.gov/graphics/se...). That person will be required to specify how long he/she will intend to stay in the US and what he/she will be doing here. In such a case, it would benefit that person greatly to have an actual customer in the region of the US that he/she was travelling to.
A second option is to obtain what the US calls a B-2 visa. This is a visa that allows a person to visit the United States for personal or medical reasons. In this case, there will be no reason to have an actual customer in the region being travelled to. However, without extensive cash resources, or proof that he/she will be receiving income to sustain him/herself from his/her job overseas, the length of his/her stay will be limited. In this case it would help if he/she had a specific like-gendered US citizen individual that he/she was going to "visit". Because, in this situation, housing and whatnot will be assumed, it is possible that the visitor would be granted a longer stay.
There are other options if he/she can claim to be employed by a US company, but I won't go into detail there.
In both of the B-visa cases, the visitor must prove extensive ties to their country of origin. This can be shown with things such as a steady job, a residence that he/she owns, substantial family, a wife or husband, children, utilities in his/her name, etc. Basically, the burden of proof is on the visitor, and the decision lies in the hands of the person performing the interview. The visitor needs to prove, without a doubt, that he/she will return to his/her country at the end of his/her intended stay.
I'm a bit of an expert when it comes to the US Visa/Immigration system... especially when it comes to finding holes and half-truths to get around the stupid rules that have been put in place.