Your thumb is nearest to you. So begin by praying for those closest to you. They are the easiest to remember. To pray for loved ones is, as C.S. Lewis once said, a "sweet duty".
On your pointing finger pray for those who teach, instruct and heal. This includes teachers, doctors, and ministers. They need support and wisdom to point others in the right direction.
The tallest finger should remind you of leaders. Pray for the president, leaders in business and industry, and administrators. These people shape our nation and guide public opinion. They need God's guidance.
The ring finger is your weakest finger; as any piano teacher will testify. It should remind you to pray for those who are weak, in trouble or in pain. They need your prayers day and night. You cannot pray too much for them.
And lastly comes your little finger; the smallest finger of all. Which is where you should place yourself in relation to God and others. Remember to pray for yourself. By the time you have prayed for the other four groups, your own needs will be put into proper perspective and you will be able to pray for yourself more effectively.