I really like Questioning Evangelism by Randy Newman. In chapter 2, "Solomonic Soulwinning," Newman gives four lessons from Solomon/Proverbs. It's very good advice. All the Scripture quotes are ESV.
1. Avoid an Argument
"Many an evangelizing Christian has won the battle but lost the war by not avoiding an ugly argument." - p 42
17:14 - The beginning of strife is like letting out water, so quit before the quarrel breaks out.
"The man convinced against his will is of the same opinion still." - p 42
2. Recognize a Fool
"...some dialogues should stop, and others should never start. Recognizing these situations before it's too late is crucial." - p 43
14:7 - Leave the presence of a fool, for there you do not meet words of knowledge.
23:9 - Do not speak in the hearing of a fool, for he will despise the good sense of your words.
18:2 - A fool takes no pleasure in understanding, but only in expressing his opinion.
"Until someone is more interested in truth than in airing his or her own opinions, it's best to talk about the weather." p 45
3. Remember that People are People
"We're not just just rational beings to be informed and educated, spiritual beings to be evangelized and enlightened, or physical beings to be fed and satiated. We are whole beings, called to love God with the whole heart, soul, strength, and mind." - p 45
"Solomon understood the complex nature of people. He realized that conveying content makes up only a small part of the communication process." - p 48
14:30 - A tranquil heart gives life to the flesh, but envy makes the bones rot.
20:5 - The purpose in a man's heart is like deep water, but a man of understanding will draw it out.
4. Remember the Power of the Tongue
10:31 - The mouth of the righteous brings forth wisdom, but the perverse tongue will be cut off.
12:18 - There is one whose rash words are like sword thrusts, but the tongue of the wise brings healing.
18:21 - Death and life are in the power of the tongue, and those who love it will eat its fruits.
17:27 - Whoever restrains his words has knowledge, and he who has a cool spirit is a man of understanding.
"...somewhere between total silence and nonstop talk lies wisdom." - p 49