The Ethiopian official was going home empty-hearted. He had not found the answers he had been searching for in Jerusalem. I wonder if anyone in Jerusalem told him about Jesus. The Bible doesn't say. But he did obtain something of immeasurable value: a copy of the Book of Isaiah.
Around noon, he was on the road south, reading from Isaiah. Philip was there, waiting to see God had in store for him. Philip ran to him and asked, "Do you understand what you are reading?" (Acts 8:30)
"How can I, unless someone guides me?" the official told him. Then he asked, "Of whom does the prophet say this, of himself or of some other man?" That was a very important question.
This is why Philip was a man who was used by God to lead others to Christ: he knew the Scripture. He could answer the question. It was an opportunity that had to be seized.
I have found that when I am sharing the gospel, when I am either preaching or speaking one-on-one, the most powerful tool I have is the Word of God. That is because God's Word does not return void. God said, "So shall My word be that goes forth from My mouth; it shall not return to Me void, but it shall accomplish what I please, and it shall prosper in the thing for which I sent it" (Isaiah 55:11).
Learn God's Word. Memorize it. Hide it in your heart. Hide it in your mind. Then when opportunities arise, you can liberally and generously quote the Scripture.