Conversation so far:
Where was Mike Piazza born?
Mike Piazza was born in Norristown, Pennsylvania, grew up in Phoenixville, Pennsylvania
What were the names of Mike Piazza's parents?
Mike Piazza is the second-oldest son of Vince and Veronica.
How many siblings did Mike Piazza have?
Mike Piazza has four brothers Vince Jr., Danny, Tony, and Tommy
What school did Mike Piazza attend?
Mike Piazza attended Phoenixville Area High School
When did Mike Piazza start playing baseball?
Mike's father saw that Mike Piazza had potential in the sport, and began encouraging his son to build his arm strength at the age of five
Who trained Mike Piazza as he was growing up?
When he was 12, Mike Piazza received personal instruction in his backyard batting cage from Ted Williams.
What opinion did Ted Williams have of Mike Piazza?
The Hall of Famer Ted Williams praised his talent, advised him not to let anyone change his swing, and autographed Mike Piazza's copy of Williams' The Science of Hitting.

Question: How did his dad encourage him?
Self-contained rewrite: How did Mike Piazza's dad encourage him?