First, find the system-of-interest
The first thing to do in systems thinking is not to think about all systems at once, but first identify the main system you want to create from scratch (greenfield) or modify (brownfield) in a project, or operate, or destroy. First, in the project, you need to find the system-of-interest: understand its function in the suprasystem and its boundaries, name it so that it can be discussed further. It is very difficult (we are talking about creative/entrepreneurial/proactive decision making, highly risky modeling of an uncertain future!), and mistakes are common and costly.
Most projects to create systems end up unsuccessful, and we only do not know about them because failures are not usually broadcasted, only successes are! The system needs to be created now, and for this, predicting its success in the future is necessary. But predicting the future with certainty is generally impossible, you can only guess (demodeling/rendering/imagination from a generative model of the world of unclear accuracy and detail---this is still "guessing" in the end)---and this is often unsuccessful, at least it cannot be done with the first guess, and multiple attempts are needed.
If you lack agility in systems thinking, you will incorrectly define the system-of-interest not only because you poorly anticipate the future, but also simply due to errors of ill-consideration. You will lose the objects that require your attention in your thinking, which will introduce risks into the project. If you define the system-of-interest incorrectly, you will simply be working on the wrong thing, wasting time unnecessarily: your focus will not be on what is important, but "near the important" or even "far from the important." Systems thinking--- is about conscious attention management, sustaining this attention on the important, defined by the types of objects in the systemic approach--- even when you are lazy, "don't feel like it", when thinking is difficult, systems thinking requires coherence (also supported by a computer: the results of system modeling must be recorded to avoid the chance of forgetting them).
The success (including commercial success) of the system being created cannot be simply "designed" and thus guaranteed (the uncertain future will always introduce its corrections, studies show that the luck factor in the success of large projects is greater than the factor of intelligence, this is explained in more detail in the course "Systems Management" in the section on strategic planning). Nevertheless, luck may be present---but there is always a chance that it will not be used due to thinking errors. Systems thinking helps to avoid thinking errors in their most probable places, helps to negotiate with a variety of people who have mastered various professional project roles and therefore anticipate various risks in advance. Systems thinking helps to track these errors throughout the project of envisioning, creating, operating, modifying, and decommissioning the system.
Timely noticed signs of possible failure will give the project team a chance to react to them in some way, including reacting by closing the project---resources should not be spent on a project that is knowingly unsuccessful under any circumstances, and systems thinking will help identify the need to close the project earlier. Systems thinking is like the forest's sanitation: it immediately kills the obviously dead project, saving the time, nerves, and money of all participants in such a project.
But systems thinking also helps find ways to continue the project, increasing the likelihood of its success---it suggests what should be the first thing to consider, what to spend time thinking about the future system. Systems thinking not only helps overcome problems, but also timely identifies problems, draws attention to them (literally: it's about attention management!). And then? Then there is systemic creativity: in the case of identified conflicts and contradictions, one must make an assumption about a possible solution. It is important to remember that there is no one correct solution, there are a huge number of solutions, but all of them are suboptimal, and the best available solutions are roughly equal in quality. Major improvements are rare!
Entrepreneurship/proactiveness/activity (here the word "activity" is understood as opposed to the word "inactivity", passivity) is understood in fundamental disciplines not necessarily in the classical economic sense of the word (that is, systems are created and developed not necessarily out of a desire to earn money, investing today in resources with low value, and then getting more tomorrow for processed resources with a higher value). Nevertheless, any activity in the project, coming from the fact that all plans are only probabilistic, the future cannot be predicted with certainty, makes both engineers-technicians, and managers as engineers of the organization with these engineering technicians, and investors in these organizations, and politicians occupied with systems of higher levels, think about how ultimately the system-of-interest will be used in its environment and what other effects from this usage may arise, maintain attention to the situation of using the system-of-interest and monitor what is happening around this usage, although this usage will only happen in the future.
When designing their systems, all engineers imagine them working--- without this, there would be no engineering! There would be no classical engineering, no enterprise engineering, no social engineering! The uncertainty of the future does not eliminate the need to have a generative model (that is, a model by which you can generate an image of the future as a version of its embodiment with certain parameters), from which you must imagine/render/generate an image of this future and imagine all possible pleasant and unpleasant surprises in this future!
In systems thinking, it is necessary to always think about the system in its systemic environment (time of usage!) and about the opinions of external project roles along the entire creation chain (external project roles must be willing to pay for the creation and/or modernization of the system-of-interest and the systems of its creation, but we also remember those external roles that will consider the project unethical, no matter how much you are promised for its implementation. No one creates a system if it is not needed (that is, if the behavior of the system in the suprasystem is not needed by anyone, if the function of this system is not needed by anyone's suprasystem to a sufficient extent to justify the costs of creating the system), if the system is knowingly unsuccessful for commercial or ethical reasons---it is not made.
But before trying to evaluate the success of the system, it needs to be found/identified/discovered. This is strategizing, the entrepreneurial/proactive/enactive part of engineering/activity/work.