1. It seems that God will not act on our behalf until we pray. Ezekiel 26:37, Matthew 6:8 - Even when He is saying that He knows what we need before we pray, He is mentioning expecting that we will still pray.
2. It seems that God wants us to ask about the same things that we have asked for before. 1 Thessalonians 5:17, Luke 18:1,7-8
3. Even though God wants us to keep asking, it seems that He finds some prayers boring and repetitious. Matthew 6:6-7
4. It seems that some prayers need to be very long and others very short. Mark 1:35, Luke 6:12-13, Matthew 26:40-41 - So when should we pray for a long time and when should we pray for a short time? From Jesus' example, He prayed ling when He was going to take big decisions - like when He was going to choose the disciples, or when He was going to encounter challenging times - like when He was about to go to the cross.