Prayer is an expression of faith in God in at least three ways. We must believe God is real. We must believe God hears our prayers.
The Bible is a book overflowing with promises. Most of them are promises God has made to his children. For example, if you're facing a big decision, God makes a promise to you in Psalm 25:8-9.
"Pray without ceasing." (1 Thess. 5:17) Few Christians object to the priority of prayer. Yet many feel like they don't know how to pray or battle a constant low-grade guilt over not praying enough.