Ask questions in your communications. Get a complete understanding of the problem or the issue. Get details. Make sure you know the context. For example, a traffic accident investigator will speak to witnesses, measure skid marks and angles, calculate speeds and take copious notes. People who communicate using critical thinking skills also ask each other multiple questions to create a more complete understanding.
Question your own assumptions. This is one of the most important aspects of critical thinking. Raise your own biases to the surface. Communicate them with your partner to invite a rebuttal. Take your own assumption and devise a list of other possibilities that might show you your assumption was incorrect.
Seek sources. When someone makes a claim, ask "How do you know that?" In a sense, you are helping others question their assumptions.
Narrow the list of possible solutions, or perhaps what you will be doing is expanding the list of possibilities in an issue. If you try to solve a problem, use the earlier three steps to reduce your options. Look over your evidence and continue to challenge your own assumptions. Eventually you will find a resolution. If you seek greater understanding, you may not arrive at one specific answer, but you will have expanded the context of the question.