Any person from outside the European Union staying in Germany more than 90 days must apply for a visa or residency permit. This permit must include permission to work when applied for. This should be done by registering at the Standesamt-Eihwohnermeldeamt (Registration Office).
Authorities will need approval from Bundesagentru fur Arbeit (Federal Employment Agency) to grant a work visa. They will need the OK that the job being applied for cannot be filled by a citizen of an EU nation. This is part of the "Priority Principle."
When applying for a visa you will need a valid passport and identification card. You will also need to fill out the application (which can be downloaded from the Internet). You will need a letter from a sponsor who will host you or be financially responsible for you until you find employment. This may also be an employer.