For example what is wrong with the question "which is the best Anti-Virus"? If the problem is there is no best then how can the question be rephrased so that the asker can make an informed decision as to which is best for him?
You have self-answered your question:
There is no best.
The focus here lies on best. What does this adjective mean?
Of the most excellent, effective, or desirable type or quality: "the best pitcher in the league".
But what is excellent, effective and desirable for me isn't necessarily excellent, effective and desirable for another person. For instance, I like Process Monitor to get rid of viruses as I don't like to have something waste resources in the background (or consume power, etc...).
Yet another person is very much likely going to a disagree with me, Process Monitor has such a steep learning curve because just disabling some entries can render your computer unbootable. And it might not be easy to spot the viruses in the list at first. Oh, and it's something you have to do manually, so you can't schedule it and forget about it.
So fine for me, so useless for another. My best is not his / her best...
The keyword best is extremely subjective; and if you want more detail, one of the Stack Exchange community managers has written a full blog post on this subject.
random has asked a good question as well:
What's the problem that you need fixing?
Let's look at your example question:
For example my computer freezes randomly and someone suggested to check the internal temperature and recommended SpeedFan. I red that SpeedFan is notoriously inaccurate and from the readings it gives me I think it is.
I ain't seeing a problem here. Why not? Because it shows no indication of research, which makes it more like homework than a problem. I would expect such question to be closed with a simple:
Which of at least 22 alternatives have you tried? Why didn't they work?
And only if you after that still haven't found what you were looking for, you have a problem for which you can actually explain what the problem is and why you can't get it solved. This is essentially in the FAQ.
Why ask a question if you can do a search instead and directly try some solutions?
The question is "How can I rephrase it?".
- Do some homework
- Include links or search results in your question that lead to directly conflicting answers.
- Use quotes from the links a lot, because links go away sometimes.
- Pose your real question: Which authority is more reliable (in this very specific aspect) here?
Even the commentary on a question that gets closed can be enlightening. Keep in mind that you probably won't be worrying about questions being closed, if you show that you did your homework.