When you were very young, did you suddenly start talking with your parents in long sentences and for great lengths of time? I doubt it. And yet they weren't disappointed in you; they were delighted in your first attempts to speak.
In the same way, when we truly understand that God is our loving heavenly Father and we are His children, then we won't worry so much about "running out of things to say" or disappointing Him. God wants us to talk with Him, our heavenly Father, and He takes delight in us when we come to Him in prayer. When His disciples asked Jesus how to pray, He replied, "This, then, is how you should pray: 'Our Father in heaven ...'" (Matthew 6:9).
Begin when you pray by thanking and praising God for His love and goodness. The Psalmist wrote, "Oh that men would praise the Lord for his goodness, and for his wonderful works to the children of men!" (Psalm 107:8, KJV). Then confess your sins and ask for His forgiveness. Finally, bring your concerns to Him. You may find it helpful to keep a list of people for whom you are praying.
Perhaps, however, the first prayer you need to make is one of faith, asking Christ to come into your life and giving yourself to Him. Christ has opened Heaven's door for us by His death on the cross, and when we know Him, we know God hears our prayers.