On a day (day of judgement) when no one and nothing could help you, the Prophet Muhammed (PBUH) can intercede on your behalf. How do we guarantee this intercession? Repeat the following dua at the end of the Adhan (call to prayer) whenever you hear it:
Allahumma rabba hadhihi-d-da‘awati-t-tammati wa-s-Salati-l-qa’imati, ati Muhammadan il-wasilata wa-l-fadilata (wa-d-darajata-r-rafî‘ati) wa-b‘ath-hu maqamam mahmudan illadhi wa‘adtahu (innaka la tukhliful mi’ad)
OH ALLAH, Lord of this most perfect call, and of the Prayer that is about to be established, grant to Muhammad the favor of nearness (to You) and excellence and a place of distinction, and exalt him to a position of glory that You have promised him.
Abdullah bin `Amr bin Al-`As [ may Allah be pleased with him] reported: I heard the Messenger of ALLAH (peace be upon him) saying, “When you hear the Adhan, repeat what the Mu’adhdhin says. Then ask ALLAH to exalt my mention because everyone who does so will receive in return ten rewards from ALLAH. Then beseech ALLAH to grant me Al-Wasilah (which is said in the dua above), which is a high rank in Jannah, fitting for only one of ALLAH’s slaves; and I hope that I will be that man. If anyone asks Al-Wasilah for me, it becomes incumbent upon me to intercede for him.” [Sahih Muslim]