Scripture does not definitively state what the best times for prayer are or how much we should do it. The Bible, however, does record the habits of many righteous people.
For example, the prophet Daniel made it a habit to pray thrice daily (Daniel 6:10). King David also did this and did so in the morning, noon and in the evening (Psalm 5:3, 55:17, 88:13, 143:8). Sometimes he would awake and offer prayer for several hours before sunrise (Psalm 119:147), a practice that was duplicated by the Lord (Mark 1:35).
David, at times, especially when he felt the trials and troubles of life were pressing hard against him, cried out to the Lord both during the day and night (Psalm 88:1). Jesus took time to pray all night before he selected twelve men to follow him (Luke 6:12) and offered supplications to the Father in the night he was arrested (Matthew 26:36).
The early church was devoted to prayer on a regular basis (Acts 2:42). The apostle Paul and Silas did so at midnight while they were together in a Philippian jail cell (Acts 16:25). Paul stated he never failed, whether during the night or day, to remember his faithful friend Timothy in all his prayers (2Timothy 1:3).
Paul regularly encouraged others to talk, as much as they could, with the Eternal (Romans 12:12, Philippians 4:6, Colossians 4:2, 1Timothy 5:5). In fact, Paul goes so far as to call upon believers to "pray unceasingly" (1Thessalonians 5:17). Clearly, we ought to communicate with our Maker as many times as we can.
What guidelines are in Scripture regarding what should be discussed during prayer? The Bible states we can make requests for ourselves (Genesis 24:12, Matthew 14:30, Luke 23:42), which includes asking that we be saved from Satan's deceptions and destructive powers (Matthew 6:13). We, of course, should also ask in prayer that such protection be extended to our family, friends and acquaintances.
Jesus, on the night on which he was betrayed, revealed to Peter and the disciples that the devil made a bold request of the Father. According to the Lord, Satan "demanded to have all of you, to sift as wheat" (Luke 22:31 - 32, HBFV). His amazingly audacious request sought to not only DESTROY the lives of the disciples but also to thwart the Godhead's goals (see Revelation 21:14)! Christ's prayer, however, that his disciples not be tempted above what they could handle (except for Judas), a request which the Father fulfilled.
We should always offer prayer to God for the safety and well-being of children (Matthew 19:13) as well as all those who are fellow Christians (Ephesians 6:18, Romans 1:9, James 5:16).
Those who have dedicated their lives to serving God and preaching the gospel should also be remembered in our prayers (2Corinthians 1:11, Ephesians 6:19 - 20, Colossians 4:3 - 4, Philippians 1:19). We should pray for those with the responsibility of governing (1Timothy 2:1 - 2).
Those who are mature in the Christian faith should be willing to visit, anoint with oil, and pray for Christians who are sick (James 5:14 - 15). Perhaps one of the hardest things we should ask for is the well-being of those who abandon us, who hate us, who use us for their own selfish goals, or who even go so far as persecuting us for our faith (Matthew 5:44, Acts 7:59 - 60, 2Timothy 4:16).
Last, but by no means least, it is always acceptable to ask for God's will to be carried out by people and for the speedy arrival of his Kingdom upon the earth (Matthew 6:10). Ultimately, the best time for prayer is anytime you feel its needed!