How can one fulfill the pledge to support God's religion in a way that pleases God and His Messenger?

Your question is similar to what Mu'adh (may Allah be pleased with him) asked the Prophet (peace and blessings of Allah be upon him). The Prophet (peace and blessings of Allah be upon him) informed him of deeds that lead to Paradise and distance one from Hellfire, which are: worshipping Allah without associating partners with Him, establishing prayer, paying zakat (definition), fasting Ramadan (definition), and performing Hajj to the House. He then guided him to the gates of good: fasting is a shield, charity extinguishes sin, and a man's prayer in the depths of the night. Then he informed him of the head of the matter, its pillar, and the peak of its hump: the head of the matter is Islam, its pillar is prayer, and the peak of its hump is jihad. Then he explained to him the importance of guarding the tongue, and that most of what casts people into Hellfire are the harvests of their tongues. So, adhere to what is mentioned in this hadith (definition) regarding the gates of good, purify your intention for Allah, and it is incumbent upon you to offer sincere advice for Allah, for His Book, for His Messenger, and for the leaders of the Muslims and their common folk.