Generally speaking, it's much easier for us to understand what it means for God to bless us, but how can we bless God, as Psalm 103 admonishes? David begins: "Bless the LORD, O my soul, and all that is within me, bless his holy name."
We bless God when we give Him the honor due Him.
C.S. Lewis thinks of it this way:
“I think we delight to praise what we enjoy because the praise not merely expresses but completes the enjoyment; it is its appointed consummation. It is not out of compliment that lovers keep on telling one another how beautiful they are; the delight is incomplete till it is expressed. It is frustrating to have discovered a new author and not to be able to tell anyone how good he is; to come suddenly, at the turn of the road, upon some mountain valley of unexpected grandeur and then to have to keep silent because the people with you care for it no more than for a tin can in the ditch; to hear a good joke and find no one to share it with. . . . The Scotch catechism says that man’s chief end is ‘to glorify God and enjoy Him forever.’ But we shall then know that these are the same thing. Fully to enjoy is to glorify. In commanding us to glorify Him, God is inviting us to enjoy Him.”
― C.S. Lewis,
Psalm 103 will be our sermon meditations from now until Lent. Let's all commit the psalm to memory. Here's the New King James Version, but learn whatever version speaks to you the most:
We need to count our blessings and deliberately think on all His benefits.