If you have no idea which profession you want to learn and practice, you can get some ideas by doing a test on the website of the Employment Agency. The so-called "career self-examination tool" ("Ekundungstool" or CHECK-U) help you find out which vocational training or degree programs might suit you. The test is designed to identify your talents and interests and then proposes fitting occupations accordingly. Keep in mind that to take the test you need sufficient German language skills.
You can take the test in the Vocational Information Center (BIZ) in your area. You can go to the BIZ without prior registration and do both tests at their computer workstations free of charge.
At planet-berufe.de, you can find out your strengths and interests and find suitable vocational training programmes and professions (in German).
If you already have work experience in your home country but do not have a (recognised) professional qualification, there is a test you can take on myskills.de to find out what professions in the German job market fit your skills and knowledge. You can ask the staff at the Jobcentre or Employment Agency for more information about myskills. Your test results can help to find a suitable job offer and they may translate to further qualifications for you. You can make an initial test at home in advance under www.meine-berufserfahrung.de. The tests are available in 12 different languages (German, English, Arabic, Russian, Turkish, Farsi, French, Spanish, Portuguese, Polish, Bulgarian and Romanian).