As a general rule non-EU nationals need a residence title (visa or residence permit) to take up employment in Germany. By law the residence title has to give information whether and to which extent access to the labour market is granted. This information replaces the former work permit. If you intend to commence work in Germany you have to apply for a visa with the competent German mission abroad before entering Germany. (Only nationals of Australia, Canada, Israel, Japan, New Zealand, South Korea and the United States may apply for the necessary residence title after arrival in Germany.)
Details as to which documents have to be presented with your visa application are available on the webpage of the competent German mission abroad or directly from the mission itself.
German missions abroad: Countries A to Z