There is an employment agency with several local service points and support via the internet to help you finding a job. There are also several organisations who offer assistance, for further information, please consult:
http://www.bamf.de/DE/Willkommen/ArbeitBeruf/Arbeitssuche/arbeitssuche-node.html
At first, you have to find out whether you are allowed to work in Germany. As a refugee, you need a recognised protection status to choose a job the same way as local citizens. If you are an asylum seeker or “Gedulded” (being allowed to stay without the status as a refugee), you might get the allowance to work. You can find the regulation in the law for asylum for example in §61. As an asylum seeker, you might get an allowance to work after three months. It is necessary that you do not live in an “refugee camp” (Aufnahmeeinrichtung). There are circumstances that force you to stay in those camps, therefore you cannot search for a job.
The immigration authorities do consult the employment agency before they grant a work allowance. They have to check the consequences for the local job market, whether a German citizen or an EU citizen might apply for the job in question and if the job has working conditions and payment as usual in the given area. When you are in Germany for at least 15 months, the first to criteria do not apply anymore. If you are for at least four years in Germany, the employment agency does not have to be consulted concerning the work allowance. Please make sure, if the regulations have changed in your case!
As an asylum seeker or “Geduldeter” you cannot be a self-employed person and run your own business.