How to Respond
This is a difficult objection to resolve through a simple answer. Many people have specific objections that they have picked up through an article on the internet or from a book. It may help to ask the person to name one of the contradictions and answer that one specifically. If you don't know the answer to the objection, be honest but be confident.
No supposed contradiction has stood the test of time. Explain that the Bible comes from writers in many different cultures writing with different languages and genres. Many of the supposed contradictions come from different ways of reckoning time, discussing regal succession, and other culturally defined subjects. Even in historical accounts the writers were documenting the history of how God has interacted with His people, not the day-to-day history of the Jewish kingdom. Details may sometimes be left out, but this does not mean that the account was false.