How to express your gratitude to the prophet Muhammad?

Our prophet, saw, took this Ummah from the murk of shirk to the light of Islam and Tawheed. This, however, came at a cost! The very bare minimum, is to be more deserving of His efforts!  
Follow His Sunnah and Obey him
“O you who believe! Obey Allah and His Messenger, and do not turn away from him when you hear him speak.” Al Nisa 59
Narrated Abu Huraira:
Allah's Messenger (saw) said, "All my followers will enter Paradise except those who refuse." They said, "O Allah's Messenger (saw)! Who will refuse?" He said, "Whoever obeys me will enter Paradise, and whoever disobeys me is the one who refuses (to enter it). Bukhari
Venere and wholeheartedly Love him!
“Say: If your fathers, your sons, your brothers, your wives, your tribe, the wealth you have gained, the trade you fear may slacken, and the home you delight in are more loved by you than Allah and His Messenger and striving in His cause, then wait till Allah brings about His command. Allah guides not the corrupt.”  Surah Al Tawbah 24
Narrated Anas:
The Prophet (saw) said "None of you will have faith till he loves me more than his father, his children and all mankind." Bukhari
Send blessings of peace (Salam) upon him
“Allah and His angels send blessings upon the Prophet. O you who believe! Send blessings upon him and salute him with a worthy salutation.”  Surah Al Ahzab 54
Allah will send blessings on you! He (saw) says:
“Whosoever invokes one blessing upon me, Allah will send ten blessings on him.” [Sahih Muslim]