For a B-1 or B-2 Visa, you apply to a US consulate in your country of residence.
In general, you apply for a visa to the US in your current country of residence. In Germany, for example, you can apply at the US consulate in Frankfurt on Main, Berlin or Munich. In Austria you can apply at the Consulate General in Munich, in Switzerland at the US consulate in Bern.
Important: Since 2001 all applicants from age 14 through 79 are required to apply in person. That means you have to schedule an appointment at the US consulate for a personal interview. Do not mail your application in advance. (Exception: persons under the age of 14 or over the age of 79 may apply by mail.)
So, first of all, please schedule an appointment for an interview, check your local US embassy website for details. Normally you should not have to wait more than a few days or up to one or two weeks as the case may be for your appointment. During the main travel seasons (summer and winter), however, it is possible that you will have to wait for up to four weeks. Please schedule your appointment well in advance since US officials can and will not take individual travel arrangements into consideration.
Every applicant needs to pay an application fee of at present 130 US$ (=98.25 Euro), which you can usually pay online. Even if your visa is denied, this money will not be refunded.
Due to the new US security laws, applications are under a greater degree of scrutiny today, so please make sure to prepare your application as carefully as possible. In addition to submitting the common application forms and paying the fee, applicants generally have to provide evidence of strong professional and personal ties to their country of residence (not the US!) and their intention to return there at the conclusion of the stay.
Should the consular officer find reason to suspect that you intend to immigrate into the US or to start working in the US, your application will almost certainly be denied. Especially applications of foreigners who have only lived in their current countries of residence for a short period of time are subject to special scrutiny.
No reasons have to be given for a visa denial. Once your application has been denied, it can, in many cases, take several months or even years before you can reapply for a new visa.
In the German-speaking countries, US consulates issue a combined B-1/B-2 Visa that can be used for both business and tourism.
Please note that the consulate will keep your passport after the interview and return it to you by mail after a processing time of approx. 1-2 weeks. Only in some exceptional cases is it possible to pick up your passport in person the next day. For that, you have to check directly with the consular officer. It is not possible to get your visa immediately the same day!