In this psalm the writer calls out for deliverance from his distress and praises God for deliverance.

The petition and complaint section of Psalm 71 are vss. 1-4, 9-13, 18, and the statements of trust and praise are in vss. 5-8, 14-17, 19, 24.

God's righteousness is emphasized in the Psalm- 71:2, 15, 16, 19, 24. 
The words "continually" in vs. 3, 6, 14 and "all day long" in vs. 8, 15, 22 are a couple of the key words and phrases throughout the Psalm.