Students: If you have a student visa, you are allowed to work during your studies for a total of 120 days per year (or 240 half-days). This is stated on your visa. This does not apply, though, to students still attending preparatory courses for the DaF Test while the courses are running. (If you have a break in between courses you can work and only with the consent of the Federal Employment Agency and the foreigners' authority.)
Graduates: After successfully completing your studies you have exactly 18 months to find a suitable job. The 18-month period starts on the date of your final Certificate of Examination! Gainful employment without restriction is permitted during the job search phase.
The Career Center on the university campus can provide information on how to find work and offers career support.
Within the context of a program entitled "Returning Experts", the German Government offers targeted support to employ graduates returning to their country of origin in development aid projects.