It is a good and Christlike desire to bring someone else before the Lord and to want to be led by the Holy Spirit as you do it. That desire itself reflects what Scripture teaches about intercession, that prayer moves beyond our own needs to bring others, our community and the world before God so that He may work.
Scripture says as many as are led by the Spirit of God, they are the sons of God. That truth invites each of us to make a personal inventory and ask, is my life truly led by the Spirit. The evidence that we belong to Him is not only that we claim to be His, but that we seek to know His will, to follow it, and to walk in step with Him. Before we were in Christ we were led by other things, by our own passions and desires, but when we are born again our spirit is made alive. God is Spirit, and when His Spirit dwells in us, His Spirit bears witness with our spirit that we are His children. That brings a glorious assurance, and if we are children then we are heirs with Christ.
Jesus Himself is our example in this. He was filled with the Spirit, led by the Spirit, and empowered by the Spirit for ministry. In the same way God desires that we be filled and led and empowered, not living after the flesh but walking in the Spirit. When we walk in the Spirit we will not fulfill the desires of the flesh, and the fruit of that walk, love, joy, peace and the rest, becomes evident in our lives.
Your prayer for someone you know is part of that walk. The purpose of prayer is not to get our own will done, but to accomplish God's will. Prayer begins with God. He lays His purposes and burdens on our hearts, we offer them back to Him in prayer, and He answers according to His wisdom and love. For that reason the most effective intercession is sensitive and open to the Spirit, listening for His leading about how and what to pray.
If the person you are praying for does not yet know Jesus, the greatest need is that they would come into that relationship as a child of God through faith in Christ alone, for only then can they call God Father and know the full blessing of prayer and of being led by Him. If they do know Him, the need is that they too would be led, strengthened and kept in close communion with Him.
May the Lord keep you walking in the Spirit in close fellowship with Him, with the assurance that you are His child. And may He use your intercession as real power for good in that other person's life, far more than we can see.
Let us pray together. Father, we thank You that You have adopted us through Jesus Christ and given us Your Spirit so that we can cry Abba, Father. We bring this dear one before You now. You know their name, their needs and their heart far better than we do. We ask that Your will be done in their life. If they do not yet know You, draw them to Yourself, show them their need for Your mercy and bring them to salvation through Jesus alone. If they do know You, fill them afresh, lead them by Your Spirit, guard them from the ways of the flesh and cause the fruit of Your Spirit to be evident in them. Give my friend who is praying wisdom and sensitivity to Your leading, that their prayers would align with Your purposes. Mold us both more into the image of Christ. We ask this in the name of Jesus. Amen.