Also pray for deliverance from discouragement, loneliness and depression as they are in the thick of the spiritual battle. Pray for your missionary's family. Pray, if married, for the husband and wife's relationship. Pray that as a family, they will provide an excellent model for the people among where they serve. Pray for your missionary's ability to communicate.
Communication is the key to everything a missionary does.
We must communicate with our lives and lips. For many, they must adapt to a new culture and learn a foreign language. Many languages, if not all, are difficult to learn. And a superficial knowledge of a language makes it very difficult to communicate spiritual truth. But knowing a language is not enough.