How to detect where am I biased and what is a tolerable amount of bias?

Ask yourself if you next decision is based on your opinions or on fact. Then check to make sure your facts are not actually your or someone else's opinions.

What is tolerable is kind of up to you. Opinions are not bad and can allow one to make "educated guesses" that speed decision making.

Recognizing that our opinions are not facts though is the first step to detecting and mitigation the many forms of bias out there.