Have patience.  There may be a silent period.  Imagine how you might feel if you just got to a new country and were thrown into a school where the teacher and most/all of the students spoke a different language.  It could be a frightening experience, right?  Your new student may spend a period of time just observing his/her new environment.
http://www.ascd.org/publications/books/106048/chapters/How-Students-Acquire-Social-and-Academic-Language.aspx
Lower their affective filter:
http://eldstrategies.com/affectivefilter.html
http://www.colorincolorado.org/glossary/affective-filter

When sharing out in a whole group situation, newcomers may want to use their Right to Pass.  If they feel comfortable, ask them if they want to share in their home language.  Even though they may have acquired basic communication skills in English (BICS), they may not be ready to use their academic language skills (CALP).  On the other hand, there are certain ELLs who may not push themselves to practice their newly acquired English skills.  Please encourage these ELLs to ask or answer questions in English, especially after some time has passed.
http://www.colorincolorado.org/article/how-create-welcoming-classroom-environment

Here is an excellent article about 6 things you should NEVER say to your ELLs:
https://www.middleweb.com/36252/6-things-we-should-never-say-to-our-ells/​