How to meet people and talk to strangers.
Always Talk to Strangers: 3 simple steps to finding the love of your life. By David Wygant. I bought this book in "essentially new" condition on Amazon from a third-party seller for $2.84 plus $3.49 ship. (You pay Amazon, Amazon pays them, they ship the book. Very safe.) Amazon's price for a new copy $10.74.
I highly recommend it. It's about how to meet people, how to prepare yourself and your attitude, where to meet people, and how to strike up conversations. You could even say it has lesson on how to be "sweetly bold" or "bold but not overbearing." The book is geared towards dating. But I think the social skills taught are also applicable towards missionary work. Buy this book for your teenage son or daughter. They'll think it will help them get dates, but it will also be preparing them for being a missionary.