TLDR; there is no way.
One thing the Coronavirus crisis has made vivid is that no one knows anything for sure. The fact that no one knows anything bubbles up every time there is a crisis. This time though, due to the severity of the mess, it is stark; in your face.
Experts used to say that eating fat is unhealthy. Now, not so much. Not long back, scientists used to believe that the adult human brain is static—once we enter adulthood, our intelligence stops improving. Today, everyone talks about brain plasticity—how the brain keeps growing with the right input even in adulthood and adapts well into old age. The scientific community is staring at a replication crisis—researchers are not able to consistently reproduce experimental results. Marshmallow experiment—one of the most cited psychology experiments, is under doubt.
When I started putting my thoughts in public, I was hesitant. I always had a voice in the back of my mind asking: How do you know you are right? I face the same when someone comes to me for advice. I am guarded with my advice.
How do I reconcile with this?
I have benefitted immensely from the thoughts of others. I am thankful to all these people who take the pain to put their ideas in front of everyone, especially in the current environment where trolling is given. Today, it is fashionable to call anyone and everyone a virtue signaller. Thankfully, I have not gone through the trolling experience as I have a tiny audience.
What is wisdom?
Wisdom is knowledge synthesized with life experiences. By studying, observing, and paying attention, one gains knowledge. One accumulates life experiences by doing. When you mesh the two together and contemplate, you gain wisdom. If no one broadcasted their thoughts, the world would be a sad place.
Strong opinions, Weakly held
An excellent framework for better thinking is: Strong opinions, weakly held. The idea is not to be married to your views. In the face of disconfirming evidence, update your beliefs. Interestingly, even this maxim is under debate.
There is no way for you to be a hundred percent sure of anything; this applies when you give and receive advice. The best you can do is color your knowledge with your life experiences and share it with others in the hope that the other person takes something positive out of it—a small way for you to give back to the society.
Always be skeptical.