1 Corinthians 14:2 tells us what happens when we pray in other tongues!
2 For one who speaks in an [unknown] tongue speaks not to men but to God, for no one understands or catches his meaning, because in the [Holy] Spirit he utters secret truths and hidden things [not obvious to the understanding]. AMP
Praying in other tongues is very powerful prayer! The Holy Spirit knows all things, especially what and how to pray for every given situation! When we pray in that Holy Spirit given prayer language, we pray for things WE don't know about, so our human minds cannot get in the way! If there is a need to pray something out in our known language, the Holy Spirit is well able to lead us in that! Then, after we have prayed in the Spirit, the best prayers that we can pray for others are found in Ephesians chapter 1, Ephesians chapter 3 and Colossians chapter 1.
Eph 1:17-23[For I always pray to] the God of our Lord Jesus Christ, the Father of glory, that He may grant you a spirit of wisdom and revelation [of insight into mysteries and secrets] in the [deep and intimate] knowledge of Him, 18 By having the eyes of your heart flooded with light, so that you can know and understand the hope to which He has called you, and how rich is His glorious inheritance in the saints (His set-apart ones), 19 And [so that you can know and understand] what is the immeasurable and unlimited and surpassing greatness of His power in and for us who believe, as demonstrated in the working of His mighty strength, 20 Which He exerted in Christ when He raised Him from the dead and seated Him at His [own] right hand in the heavenly [places], 21 Far above all rule and authority and power and dominion and every name that is named [above every title that can be conferred], not only in this age and in this world, but also in the age and the world which are to come. 22 And He has put all things under His feet and has appointed Him the universal and supreme Head of the church [a headship exercised throughout the church], [Ps 8:6.] 23 Which is His body, the fullness of Him Who fills all in all [for in that body lives the full measure of Him Who makes everything complete, and Who fills everything everywhere with Himself]. AMP
Eph 3:14-21 For this reason [seeing the greatness of this plan by which you are built together in Christ], I bow my knees before the Father of our Lord Jesus Christ, 15 For Whom every family in heaven and on earth is named [that Father from Whom all fatherhood takes its title and derives its name]. 16 May He grant you out of the rich treasury of His glory to be strengthened and reinforced with mighty power in the inner man by the [Holy] Spirit [Himself indwelling your innermost being and personality]. 17 May Christ through your faith [actually] dwell (settle down, abide, make His permanent home) in your hearts! May you be rooted deep in love and founded securely on love, 18 That you may have the power and be strong to apprehend and grasp with all the saints [God's devoted people, the experience of that love] what is the breadth and length and height and depth [of it]; 19 [That you may really come] to know [practically, through experience for yourselves] the love of Christ, which far surpasses mere knowledge [without experience]; that you may be filled [through all your being] unto all the fullness of God [may have the richest measure of the divine Presence, and become a body wholly filled and flooded with God Himself]! 20 Now to Him Who, by (in consequence of) the [action of His] power that is at work within us, is able to [carry out His purpose and] do superabundantly, far over and above all that we [dare] ask or think [infinitely beyond our highest prayers, desires, thoughts, hopes, or dreams] — 21 To Him be glory in the church and in Christ Jesus throughout all generations forever and ever. Amen (so be it). AMP
Col 1:9-14 For this reason we also, from the day we heard of it, have not ceased to pray and make [special] request for you, [asking] that you may be filled with the full (deep and clear) knowledge of His will in all spiritual wisdom [in comprehensive insight into the ways and purposes of God] and in understanding and discernment of spiritual things — 10 That you may walk (live and conduct yourselves) in a manner worthy of the Lord, fully pleasing to Him and desiring to please Him in all things, bearing fruit in every good work and steadily growing and increasing in and by the knowledge of God [with fuller, deeper, and clearer insight, acquaintance, and recognition]. 11 [We pray] that you may be invigorated and strengthened with all power according to the might of His glory, [to exercise] every kind of endurance and patience (perseverance and forbearance) with joy, 12 Giving thanks to the Father, Who has qualified and made us fit to share the portion which is the inheritance of the saints (God's holy people) in the Light. 13 [The Father] has delivered and drawn us to Himself out of the control and the dominion of darkness and has transferred us into the kingdom of the Son of His love, 14 In Whom we have our redemption through His blood, [which means] the forgiveness of our sins. AMP
Pray these prayers for yourself and others, putting your name and theirs in the place of the "you" in these, at least once a day for a month and see for yourself how God answers these prayers! Amen! Here is "Desert Song" by Hillsong:
Shalom in Him!
