Here is a good article on evangelism from the Slice of Laodicea blog, with a good quote from the late Dr. Martin Lloyd-Jones, which I will replicate here:
The whole purpose of evangelism is primarily to tell men what sin has done to them, to tell them why they are what they are, namely, separated from God. It is to tell them that what they need above everything else is not to be made to feel happy, but to be brought back into a right relationship with the God who is 'light and in him is no darkness at all'. But that means preaching holiness. To separate these two things, it seems to me, is to deny essential biblical teaching.
— Martyn Lloyd-Jones, Exposition to Ephesians