Attitudes for Critical Thinking
The purpose of critical thinking is to get to the truth. Most people want to be right but few are willing to be wrong to get there.
The first thing to understand is that everybody thinks what they believe is right. By definition nobody can hold a belief that they think is wrong because a belief is something that you believe is right. Finding the truth requires that you be open to the possibility that your belief is wrong otherwise you will never change your belief. This does not mean that you change your belief every time a new idea is proposed but that you at least consider that new idea. Remember that any point of view will seem right until it is challenged. However, you actually need to listen to the other side, not just someones opinion of how the other side is wrong. I would suggest reading books or asking questions to somebody who actually believes it.
The next step is understanding the importance of each belief. There are certain beliefs that are foundational and should require a lot of evidence before changing. There are other beliefs that are minor which don't require much evidence at all. For example, believing that Jesus Christ died for your sins is an important foundational belief. It should take a lot of evidence before you change that belief. On the other hand, believing that Coke is better than Pepsi is not a foundational belief and it can be changed by simply trying both at the same time. Be careful not to invert the importance of a belief. Being willing to die for you belief that Coke is better than Pepsi would be a very foolish thing!
Having a humble mind and an understanding of the important things in life will give you a foundation on which to build your critical thinking. If you don't do the two things mentioned above then critical thinking will be of no use to you since your eyes will be closed to the truth. It is also important to understand the context in which you are living and apply consistent principles. The society we live in influences us more than we would like to admit. How many people will actually like the song Gangnam Style in 1 year, even though it has had over 1 billion views? To mitigate these influences it is important to be consistent. Inconsistencies in our approach will show us our blind spots. The same country that gets outraged when turtle eggs are destroyed is the same country that supports killing babies that have not been born. The same country that religiously believes in natural selection is the same country that supports non-reproductive relationships. The same country that supports no fault divorce is the same country that talks about love.
Finally, don't force a belief just because it is what you want to believe it. This type of self-deception compromises everything else you believe because you are willing to lie to yourself. If you have doubt about something then it is probably best to leave it until you are confident that the belief is true. There is no shame in saying I don't know. Knowing that it is possible we could be wrong, understanding that not all beliefs are as important, and admitting that we are influenced heavily by our context will enable us to think critically about what we believe.