Since recently OpenAI have introduced custom instructions where you can provide specific details and guidelines for chats (see https://openai.com/blog/custom-instructions-for-chatgpt )
What have you used?
At first I added a lot, but I toned it down because I felt chatGPT would sometimes focus on that unnecessarily.
Now I only have my country and languages, and I have requested any answers to be in metric units. That last one is very useful when I ask for recipes, before it would talk about Fahrenheits and Ounces and what not. Now I at least get Celcius, milliliters and grams!
I also added that it should reply as an expert in the field with a casual tone. Which causes it to go “aah, the old … problem” whenever I ask it for debugging help :D
I occasionally use this
use markdown to organize your thoughts boilerplate is often unhelpful. Off topic explanations are unhelpful, (unless its an opinion) don't explain unless asked.i often find it flavors chatGPT’s output beyond adding (unhelpful amounts of) markdown