What are the types of hidden or minor shirk and how can one be saved from it?

Subtle polytheism (shirk (definition) al-khafi) is a type of minor polytheism, manifested in ostentation (riya'), swearing by other than Allah, clinging to unlawful means such as wearing amulets with the belief that they benefit or harm, attributing protection or care to created beings, like saying, "Were it not for the guard, the money would have been stolen," and conjoining the will of the servant with the will of Allah using the conjunction "wa" (and), as in "Whatever Allah wills and you will."

To guard against minor polytheism: 1. Frequently recite the supplication: "O Allah, we seek refuge in You from associating anything with You knowingly, and we seek Your forgiveness for what we do not know." 2. Feel the ugliness of polytheism, no matter how minor. 3. Understand that it nullifies deeds or diminishes their reward. 4. Realize that ostentation (riya') causes its perpetrator to fall in the estimation of people.