Pretty regularly I have an issue of not knowing how to pray for those I love who aren't walking with God. I'm distracted with thoughts, or I'll say a few things that I really desire for them and then I'm unsure what else I could be bringing to God about it. I'd like to spend a good amount of time pleading with God for mercy towards them and converse with him about how to trust him when I'm unable to be the one to renew their heart.
God has led me through Psalm 51 to pray someone I love deeply. Praying through Psalm 51 makes you cry out for God to show mercy, to help them delight in truth, to blot out their iniquity, it shows you to plead with God to not hide his face from them or remove his Holy Spirit. It reminds you that if God extends his mercy they can be whiter than snow. It helps you to remember to pray that they wouldn't look to any good work to either please God or to be made right with him. Psalm 51 reminds us that we are completely dependent upon God to save them, to see their sin against him and only him, and God alone shows them that there is no real or lasting joy outside of walking with Him.
It may bring a few tears as well.