Psalm 100:
Psalm 100 is a familiar one to almost all of us. It is called a Psalm of praise. We see Elohim’s goodness in all his works. In it we find the duties of a godly man.
“Psa. 100:  1 Make a joyful noise unto the LORD, all ye lands.

1. Serve the LORD with gladness: come before his presence with singing. 
2. Know ye that the LORD he is God: it is he that hath made us, and not we ourselves; we are his people, and the sheep of his pasture. 
3. Enter into his gates with thanksgiving, and into his courts with praise: be thankful unto him, and bless his name. 
4. For the LORD is good; his mercy is everlasting; and his truth endureth to all generations.”

Praise Him: The first thing that we see is that we have to praise him. We praise him because he is our Creator, Sustainer, Provider and great Redeemer of our sinful lives. We can praise him only when we know him personally for all the good he is doing in our lives. Praise makes the Lord happy, he enjoys it. Praise makes a throne for the Lord to come closer to us. Praise helps us to escape temptations, it protects us from temptations. We should express our gratitude to the Lord loudly and publicly. Make a joyful noise to the Lord! The Psalm is calling on the people of the Lord to praise Him from their hearts. We should publicly praise the Lord, in spite of what others may think.

Serve Him:  The word service means to be in bondage to someone and doing whatever he tells us to do.  We belong to the Lord. Elohim is all-powerful and all-knowing. He has created this world and all that is in it. Everything belongs to him, so what can we give in return for what he has done? We should serve the Lord with all the talents He has given us and use them to glorify Him. We should serve him with singing and joy. Serve him (by sacrifice) with all your heart, soul and spirit. Use your talents like singing, helping the poor and needy, showing mercy to those who are struggling to make both ends meet, spreading the gospel, etc. We should help in establishing the Kingdom of Yahweh on this earth. Serve the Lord with gladness.

Thank Him: We should thank him for all the good that he has done in our lives, count all the blessings we received from our birth till date. We should show our gratitude to him. We thank people for small things they do to us, how much more should we be thankful to our great Lord! We should start thanking him for the gift of life that he has given us, for the air that we breathe, for the days and nights, for all things that make our life comfortable. Above all, we should be thankful for giving us his Son and his Son’s blood to wash our sins away and giving us eternal life.

Worship Him:  1Ch 16:9: Sing unto him, sing psalms unto him, talk ye of all his wondrous works.
The apostle Paul tells in Romans 12:1-2: “I urge you therefore, brethren, by the mercies of God to present your bodies a living and holy sacrifice, acceptable to God which is your spiritual service of worship.” This is true worship.
Worship him because he is our Elohim and there is no other Elohim. We are his people and He is our King to rule over us. He is the potter and we are the clay(Isa.64:8, Jer.18:4). He made us and not we ourselves. He provides for all of our needs, like a shepherd who provides food, shelter, water, takes care of the sheep-He give us peace like still waters. We worship him because he is the way, the truth and the life.(John.14:6). We worship him because He is a merciful Elohim (kind and forgiving). We are alive today because of His mercy and kindness. Though we sin, he still forgives us if we ask and repent for our sins. He is kind and helps all those who need his help. Turn to Him and He will turn to you (Mal.3:7).
True worship should be centered only on Elohim. Too often we get caught up in small, unnecessary details like the type of music we should have, the sound system, the stage setting, etc. We give importance to the form of worship than the spirit of worship. We should worship only Yahweh Elohim but not Mary the mother, saints, idols, statues, or other persons. True worship is acknowledging Elohim  and his power and glory in all that we do.

We should be thankful to Him simply because He is good. He is gracious, kind, bountiful, forgiving, just, faithful, merciful, and loving. His grace is everlasting. Grace is favour he shows on his beloved and fills us with everlasting love. He created man with his own hands and wants to have fellowship with man. His truth is seen In all generations till today. He is Elohim who changes not (Mal.3:6). Mercy can be defined as "getting what you don’t deserve, not getting what you deserve." His mercy will never be exhausted, Lam 3:22-23: “It is of the LORD'S mercies that we are not consumed, because his compassions fail not. They are new every morning: great is thy faithfulness.” He has made a covenant with man and that never changes.