Child allowance is usually paid when the applicant is resident or unlimited income tax payer in Germany.
Citizens from EU-/EWR member states or from Switzerland who are resident or employed in Germany can apply for child allowance right away.
People from Algeria, Bosnia and Herzegovina, Kosovo, Morocco, Serbia, Montenegro, Tunisia and Turkey can get child allowance if they are employed in a job with unemployment insurance.
All other foreigners must have a settlement or residence permit.

In addition, the child must be domiciled or normally resident in Germany or another EU member state.
Foreign parents with a residence permit in order to study, go to school or visit a language course do not benefit from child allowance.

Child allowance is payed for

• children untill their 18th birthday
• 
  
• children in school/studies untill their 25th birthday
• 
  
• unemployed children untill their 21st birthday

Child allowance is payed monthly in the amount of

• for the 1st and 2nd child 184 euro each
• 
  
• for the 3rd child 190 Euro
• 
  
• for every other child 215 Euro

The application must be handed in to the Family Office of the Federal Employment Agency in a written form.

The Federal Employment Agency or your employer in the public service (TU Dresden) will hand out the application forms which you also can downloyd here (only in German):
Application form 

Contact to the Family Office of the Federal Employment Agency:

Agentur für Arbeit, Familienkasse Bautzen
Neusalzaer Straße 2
02625 Bautzen
phone: +49 (0)1801 546337
Fax: +49 (0)3591 661878
E-Mail: Familienkasse-Bautzen(at)arbeitsagentur.de