Since Psalms are poetic, they contain parallelism and figures of speech.
The following material is based on the books:
1. Gordon D. Fee, Douglas Stuart How to Read the Bible for All Its Worth
2. How to Study the Bible (published by BEE International)
3. Fred J. Greve Old Testament Survey. A Study Guide
4. Carl B. Gibbs Principles of Biblical Interpretation
CLASSIFICATIONS OF PSALMS
Classification of psalms according to their subjects:
1. Psalms of groaning - complains to God in difficult times. There are psalms of individual groaning and psalms of corporate groaning.
2. Psalms of thanksgiving - joy and thanks to God for something positive. There are psalms of individual thanksgiving and psalms of corporate thanksgiving.
3. Psalms of praise - praise to God for who He is. There are psalms of individual praise and psalms of corporate praise.
4. Psalms on salvation history - psalms on the history of God's work of salvation in Israel.
5. Psalms of celebration:
1) Psalms of renewing of the covenant with God
2) Messianic psalms
3) Royal psalms
4) Psalms of enthronement
5) Psalms of Zion
6. Psalms of wisdom - psalms that praise wisdom and teach wisdom.
7. Psalms of trust - psalms that express trust and faith in God.
8. Psalms of repentance - psalms that express repentance in sins.
9. Psalms of curse - psalms where psalmist asks God to curse his enemies.
Classification of psalms according to the feelings they express:
1. Psalms that express feeling of pain caused by sin
2. Psalms that express sufferings because of sinners' attacks
3. Psalms that express considerations about life of righteous and unrighteous people
4. Psalms that express considerations about God's nature
5. Psalms that express recollection of God's works
There are also other classifications of psalms.
Interpreting psalms, try to find information about historic background of the psalm from the psalm itself, other books of the Old Testament, and from the literature - Bible commentaries, Bible dictionaries, and Bible encyclopedias.
Also, try to find out the subject and feelings of the psalm.