Why and when to pray?

As written in the scriptures.

Acts 6:4

4 and will give our attention to prayer and the ministry of the word.�

John 14:12-14

12 Very truly I tell you, whoever believes in me will do the works I have been doing, and they will do even greater things than these, because I am going to the Father. 13 And I will do whatever you ask in my name, so that the Father may be glorified in the Son. 14 You may ask me for anything in my name, and I will do it.

Philippians 4:6

6 Do not be anxious about anything, but in every situation, by prayer and petition, with thanksgiving, present your requests to God.

Ephesians 6:18

18 And pray in the Spirit on all occasions with all kinds of prayers and requests. With this in mind, be alert and always keep on praying for all the Lord�s people.

Romans 12:1-2

12 Therefore, I urge you, brothers and sisters, in view of God�s mercy, to offer your bodies as a living sacrifice, holy and pleasing to God�this is your true and proper worship. 2 Do not conform to the pattern of this world, but be transformed by the renewing of your mind. Then you will be able to test and approve what God�s will is�his good, pleasing and perfect will.