I'm not evangelical, but here's my take, based on personal experience as a missionary (but not a preacher).
Being a missionary requires listening far more than talking and doing far more than talking. Being an "example of the believers," being meek and humble, and answering people's questions while helping them and being the best friend you can be is the way to turn people who have deep concerns within themselves, and most people do have deep, existential concerns, whether they realize it consciously or not.
Other people need the "fire and brimstone;" they need to be called to repentance to atone for their sins directly. The approach differs per person, and ya' gotta feel it out.