Start with this Du'a
Refuge from shirk, known and unknown
اللَّهُمَّ إِنِّي أَعُوذُ بِكَ أَنْ أُشْرِكَ بِكَ وَأَنَا أَعْلَمُ، وَأَسْتَغْفِرُكَ لِمَا لاَ أَعْلَمُ
Allahumma inni a'udhu bika an ushrika bika wa ana a'lam, wa astaghfiruka lima la a'lam.
“O Allah, I seek refuge in You from associating anything with You knowingly, and I ask Your forgiveness for what I do unknowingly.”
Al-Adab al-Mufrad 716 (sahih)
Taught by the Prophet ﷺ to Abu Bakr, who was told that shirk creeps in more quietly than the footsteps of an ant.