The "I don't know" advice is great, and has done the most to enhance my technical credibility of anything. If you admit freely what you know and don't know, it helps people believe that you do know. By contrast, people who are afraid of admitting that they don't know something are always treated with skepticism.
For some reason, a lot of people seem to have been told to never show weakness by admitting that they don't know something.
I had a professor who gave 20% credit for answering "I don't know" for a question on your homework (plus a little extra if you explain what you do know and why you don't know), and I stole that rule for my own class. One of my students became the VP of a chip company, and told me that the "I don't know" homework rule helped him gain a lot of confidence and save the BS.
For some reason, a lot of people seem to have been told to never show weakness by admitting that they don't know something.
I had a professor who gave 20% credit for answering "I don't know" for a question on your homework (plus a little extra if you explain what you do know and why you don't know), and I stole that rule for my own class. One of my students became the VP of a chip company, and told me that the "I don't know" homework rule helped him gain a lot of confidence and save the BS.