How can the media influence people's beliefs in god?

Many ways. Fictional (or non fiction, if you believe them) TV shows, movies and news stories about religious phenomena such as miracles, the afterlife, heaven and hell, good v evil etc. is the most common.

Advertising subliminally and overtly. For example many non for profit organisations are suggestive of Christianity to get donations.

Individual opinion: Many TV personalities are suggestive of a good v evil concept in remarks and mannerisms, including news reporters. eg. floods are an act of god, or mother nature.

The media can also influence people beliefs in god through news Propaganda about alternative religions, politically driven stories about different cultures both locally and abroad.

On a broader scale, networks may have a ingrained culture within their operations, that shapes strategy eg. Jewish, Catholic, Protestant, New age, Darwinism, Scientology etc.

The news media in particular can influence belief in God, particularly when they report research findings in a skewed manner, as Yahoo News did when they posted an article under the outrageous headline, "Belief in God Boils Down to a Gut Feeling" (September 22, 2011). See the Sources and related links below to understand why the news article and the research is encouraging Atheism.