Preaching: Training before Preaching

                                                                  Q. If I have two options, viz.
                                                                  1) Serve someone in need i.e. help others through community service -OR-
                                                                  2) Chant the name of the God.

                                                                  Q. 1. One of the nama aparadhas (offenses against the holy name) is to preach to a non believer. Would you please elaborate on this. It's confusing me as devotees many times preach to a non believer.