Question: How can I tell if someone is ready to hear the gospel?
Answer: Begin by assuming people who are open to you as a person are usually open to hearing the gospel as well. Start talking with them, taking it one step at a time. Engage them in conversation about their family, job, and background. Then look for a way to transition into spiritual things. It may be by mentioning prayer, God, the Bible, or religion. Watch how open and receptive they appear by their comments, actions, and reactions. Keep going deeper, and go as far as you can. Should you observe little or no resistance, you can keep assuming there is an open door for the gospel. If they make it clear they would rather not talk about spiritual things, you have gone as far as you can go. Your inability to go further is because of them, not you.
One more thing. As you converse with them, whisper a prayer, "God give me boldness." God will answer that prayer. That way should you sense a person is not open to the gospel, you will know it’s because the Holy Spirit has not prepared them rather than fear clouding your judgment.