Are you jaded, and cynical of all that you see around you in the lives of Christians? Do you hear a lot of talk and see little action? Then start by reading this book: it'll rattle your cage in the biggest way, and give you an example of relentlessly following Jesus' commission to all Christians.
After you've read this, get a copy of the Self-Confrontation manual (by John Broger, published by the Biblical Counseling Foundation: (760) 773-2667) and go through it: its an excellent way to root out the many common sins of omission (not just the sin of omitting the Great Commission) and of commission. Then head for the ends of the earth.
(And no: I don't have any affiliation with BCF, other than having benefitted greatly from their training.)