While the Almighty God indeed knows all things, He still wants us to ask what we need from Him. Despite that the Lord Jesus know that Bartimaeus was blind, He still asked him what he wanted. The Lord did this in the light of the fact that He knows that our needs differ from person to person and from time to time. For instance, while Prophet Elisha wanted the double portion of Elijah's anointing, Gehazi wanted money and other worldly gifts.
Esau wanted food rather than of the right of the firstborn while on the other hand Jacob wanted the privileges of the firstborn. Some individuals ask for little things when they should be asking for things that will last for eternity.
David with all his heart sought the Lord and had only one desire in his entire lifetime: to live in the house of God all the days of his life. It is the potency of your desire for a thing that would motivate you to ask whoever can give it to you. You must also be willing to pay the price just like the apostle Paul did. Paul desired to know the Lord Jesus and so he left go everything to gain Him.
How soon you want answers to your prayer is also a thing to consider. Some individuals mistakenly postpone their season of celebration. Some folks are like Pharaoh who told Moses he would want the affliction of frogs to vanish from the land by tomorrow.
Why did he have to say tomorrow and not now? You may be asking the right thing at the wrong time and the greatest request someone could make to God is the request for salvation and it must be today and not tomorrow if you are still yet to encounter the saving grace of the Lord Jesus.
Elisha didn't waste time telling Elijah that all he wanted was the double portion of his anointing. It was a hard thing, yet he got it in the light of the fact that he knew what he wanted, why he wanted it, and when he wanted it.