Observe the finer details of everything. This is not just in relation to tangible things, but also in relation to the intangible; if someone tells you something, look at everything about what they said, the way they said it and what caused them to say it. Everything has context, and to be a successful critical thinker you should focus on this context.
Think about things from multiple angles. Everything has a different point of view; your view of, say, a refrigerator is different from someone in another room, partly because you are standing in different areas and looking at it from different angles, and partly because you both likely had dissimilar experiences with refrigerators in the past. So, to think critically you need to always consider the fact that everything looks different from a different angle.
Set criteria on which you will judge things. Critical thinking is about understanding things objectively rather than subjectively.
Follow the criteria you set above when evaluating anything. This essentially removes your emotions from the equation, which is important because critical thinking is about viewing things as they are rather than how they affect you or make you feel.
Evaluate things slowly and methodically in order to really critically evaluate them rather than making a snap emotional judgement.