"Praise the Lord!
Praise, O servants of the Lord.
From the rising of the sun to its setting The name of the Lord is to be praised." Psalm 113:1 & 3

In part, Webster defines praise as 'the offering of grateful homage in words or song, as an act of worship.'
A synonym for grateful is thankful. Thankful describes an appreciative attitude for what one has received.
Therefore, we praise the Lord with gratefulness, with thankfulness for His great love and His gift to us; life instead of death. His life! 
His eternal life!

Scripture enjoins (directs; charges) us to praise the Lord. Then we see in the following verses who, how and when we are to praise and worship our Lord. (Scripture has much to say concerning praise and worship and would be a wonderful personal study.)

All are to praise our Lord:
"Let the peoples praise You, O God;
Let all the peoples praise You." Psalm 67:3 & 5

"Sing to the Lord a new song,
And His praise from the ends of the earth..."
Let them give glory to the Lord,
And declare His praise..." Isaiah 42:10 & 12

Give praise in song and with instrument:
"Sing praises to the Lord, who dwells in Zion!
Declare His deeds among the people." Psalm 9:11

"Make melody to Him with an instrument of ten strings.
Sing to Him a new song;
Play skillfully with a shout of joy.
Sing out the honor of His name;
Make His praise glorious." Psalm 33:2-3

Our praise is to be continuous:
"Therefore by Him let us continually offer the sacrifice of praise to God, that is, the fruit of our lips, giving thanks to His name." Hebrews 13:15

And, Why? Just look at 1 Peter 2:9-10
"...You are a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light; who once were not a people but are now the people of God, who had not obtained mercy but now have obtained mercy."

Yes, we are that special people! How can we not continually praise and worship our God and Savior?!

Let us heed the exhortation of the Apostle Paul as he writes, "...Be filled with the Spirit, speaking to one another in palms and hymns and spiritual songs, singing and making melody in your heart to the Lord,  giving thanks always for all things to God the Father in the name of our  Lord Jesus Christ." Ephesians 5:18-20

Psalm 150 eloquently expresses the heart of one who joyfully, reverently, thankfully is praising the Lord.
"Praise the Lord!
Praise God in His sanctuary;
Praise Him in His mighty firmament!
Praise Him for His mighty acts;
Praise Him according to His excellent greatness!
Praise Him with the sound of the trumpet; Praise Him with the lute and harp!
Praise Him with the timbrel and dance;
Praise Him with stringed instruments and flutes!
Praise Him with loud cymbals;
Praise Him with clashing cymbals!
Let everything that has breath praise the Lord.
Praise the Lord!"

With grateful hearts we worship You Lord God Almighty! All praise and glory are Yours! Amen