If our lives are consistent, and our words godly and pure, and our love for them genuine, they will usually be open to us. As to when they respond - that is the business of God. Our job is to sow and water, and wait for God to bring forth fruit. I have asked him to come with me to church several times, but he keeps avoiding the question. Don't first share church with your friend, first share Christ.
Questions are a good way to get started.
The Fellowship of Christian Athletes has a small pamphlet called More Than Winning, which presents the gospel in a simple way. You might like to keep a few on hand to give your friends and others. We suggest you make your words few and your deeds many. Pray for your enemy. When this person is ugly to you, turn the cheek and go the second mile with them.