There are thousands, or more likely hundreds of thousands, of online resources regarding critical thinking. There are different ways to learn and use critical thinking, depending on the discipline. The definition of critical thinking seems to depend on the discipline, the school, the department, the class, the country and so on.

This military site has a fascinating description and approach for the use of critical thinking in the Air Force. This page, "DEVELOPING THINKING SKILLS: CRITICAL THINKING AT THE ARMY MANAGEMENT STAFF COLLEGE", which is referenced from this page, "Creativity, Thinking Skills, Critical Thinking, Problem solving, Decision making, innovation", is a good read. This is just one of the many resources at Air University, the intellectual and leadership center of the Air Force (US).

The State of California appears to be leading the way for students with this site, "California Critical Thinking Skills Test", which has many references from that page. It is based on what "became known as "the Delphi Report," a document which continues to influence critical thinking theory, teaching, and assessment in the full spectrum of academic disciplines and professional fields". More about this Expert Consensus on Critical Thinking can be found here. Although this report seems to contradict my statement in the first paragraph, I'll go with my statement. Why? Not everyone/organization agrees - so we still have multiple "definitions" of "critical thinking"

Ok, on to a slightly different but related topic. This involves teaching and understanding a technique for fast critical thinking and conflict management. This site uses an Awareness Wheel to help people help themselves. The blog page called, "What Goes Around Comes Around: Keep practice communication on track with the Awareness Wheel", explains it quite nicely.
There are "different" versions of an "awareness wheel", some more detailed than others, but the concept seems the same. That is, the outcome.

It seems awareness/resolution/conflict/option/ "wheels" are common for a number of quite different reasons. This one is student/school related. Have a look at this "Conflict Resolution" page, and also the Conflict Resolution Wheel for elementary school students. The Conflict Resolution Guidebook is linked from the initial page to a pdf file.

I recently attended a two day Critical Thinking workshop and I must admit that I had no idea what would be presented, as the attendees were corporate clients. It was a learning experience instead of just a what-it-is lecture. It was quite a valuable learning and doing exercise and the instructor/facilitator included maximum use of an "awareness wheel". Other techniques were discussed and used and some of the material was influenced by authors such as, Stephen Brookfield, Marilyn Herasymowych, Henry Senko and Edward de Bono. Thank you E.

Good luck...Good teaching...Good learning...

Cheers - Mike