Gratitude has three levels; an internal one, which is manifested in man's silent gratitude to Allah the Almighty for His Blessings. The second level is the verbal gratefulness, which is expressed explicitly, such as saying, "O Allah, praise be to You for honoring us, for making the means of wellbeing available to us,

for granting me a good wife, and dutiful children..". There are elegant professions that people can do, but the highest level of gratitude to Allah, it is serving others. Allah describes serving others as a way to show gratitude to Allah for His blessings. Allah the Almighty says:  

("Work you, O family of Dawud (David), with thanks!" But few of My slaves are grateful.)

[Saba’: 13]  

                   
Accordingly, there is an implicit gratitude, when one’s heart is grateful to Allah, a verbal gratitude that is expressed by praising Allah, and a practical gratitude that is reflected by serving others in gratitude for Allah’s blessings.     

Dr. Umar Abdul Kafi: 

Unfortunately, some people misunderstand the meaning of gratefulness. They think that it can be offered verbally for each single blessing. Thus, Allah the Almighty says: 
  

(And if you count the Blessing of Allah, never will you be able to count them.)

[Ibrahim, 34]

Well, I cannot be enough grateful to Allah for even one Blessing, so how about all the Blessings I am surrounded with?!

Dr. Rateb: 

This look like saying to someone, "Take this Dinar and start counting it!" As for the Ayah: 

(And if you count the Blessing of Allah…)

[Ibrahim, 34]

In the aya, blessing is mentioned as a singular noun (ni’mah). If you ponder over one single blessing, you would see that it has thousands of dimentions.