Give feedback to your Copilot colleague. Then keep giving it.

In the Microsoft 365 Copilot app, open the three dots in the top-right corner, then Settings → Personalisation. Three controls matter here. Customise Copilot holds your standing instructions. Saved memories is where Copilot keeps facts you have told it; inspect and correct them now and then. Chat history & work insights is the toggle I showed you on Friday: keep it on so your colleague learns, and use Work IQ off or a temporary chat when you want a clean room.

Open Manage under Customise Copilot and start with three lines. These are the ones from the Copilot Goodie Bag I sent Oskar before Friday; they fix the three corrections I was making most often.

Then test a familiar task in a new, ordinary chat. Keep the instruction if the result improves. These are preferences, not guarantees; if Copilot ignores one, reword it or restate it in the prompt.

Inside Excel, the Copilot pane has its own settings menu: the three dots in the top-right corner of the pane. Choose Personalization. A dialog called Customize Copilot opens with one text box. Whatever you save here follows your account into every workbook and every device, applies from your next prompt, and is never stored in the file.

Microsoft lists eight areas you can set preferences for: number and currency formatting, date and unit conventions, table style and layout, formula preferences, charts and PivotTables, conditional formatting, level of detail, and tone and wording. Short lines work better than paragraphs. Here is the set I would start a reporting manager with; edit the currency and date lines to your own habits.

Check it by changing an input: the result should recalculate. Open the formulas Copilot wrote. If a result ignores a preference, say so in the prompt and consider rewording the saved line.

This is the one I ran out of time for. Personalization is yours; workbook rules belong to the workbook. Anyone who opens the file gets them, without any set-up on their side. They live in a plain, visible worksheet named .Rules, one rule per cell in column A. Hidden rules sheets are ignored.

To create one, open the plus sign in the pane's prompt box and choose Create workbook rules. Copilot adds the .Rules sheet with a template of examples. Once the sheet exists, the same menu says Go to workbook rules. You can also just add a sheet called .Rules yourself, copy one from another workbook, or ask Copilot to add a rule for you.

Replace the template with your own rules. Short examples of the result you want beat long descriptions. Use heading cells such as ## REPORTS to group them. Three sets to copy, one per cell:

Rules can even be dynamic. Microsoft's own example puts a dropdown in cell B1 of the .Rules sheet and writes =IF(B1="Executive","Show KPI summary only","Include full drill-down tables"), so the audience selector changes how Copilot reports. Try it once; it is a neat way to keep one workbook for two readers.

Honest limits: rules are guidance, not validation. They are only fully supported in English, and behaviour can differ between models and over time. Test with a working copy, as a colleague would see it, and inspect the actual output.

A skill is a set of instructions Copilot follows for a recurring task. You call one by typing an @mention in your prompt, or through the plus sign → Choose plugins and skills. Microsoft ships a few: @clean-data finds and fixes extra spaces, inconsistent formats, duplicates and wrong data types and lets you choose which fixes to apply; @chart-design creates or improves charts; @theme-design and @brandkit handle look and brand; @skill-builder turns a workflow you just did into a new skill. There is also a folder of twenty finance skills, from three-statement models to variance monitoring.

Which ones you see depends on rollout. In my account the dialog shows Custom skills, Finance and Visualization; yours may show more or fewer.

The easiest way to make your own: do the job once with Copilot, then say

The manual way, if skill-builder has not reached your account yet: in the pane, three dots → Manage plugins & skills → Custom skills → Create skills folder → Open skills folder. Each skill is a folder in that OneDrive location, named exactly like the skill, containing a SKILL.md file. Here is a complete one you can adapt.

Skills are supported only in English and need the Office display language set to English. They cannot run code outside Copilot's own tools; scripts in a skill folder are resources, not new powers. Turn a skill off in the dialog and Copilot stops using it automatically; a direct @mention still works.

The prompt beats the saved preference. Rules travel with the file, preferences travel with you, skills run when called. Change one layer at a time, run the same task before and after, and write down what you changed and where. If a result goes wrong, it is far easier to find the sentence that caused it. That is also exactly the four-line share-back we use in the channel: I kept correcting, I changed, I checked, I will keep or remove it because.

And expect to come back. A preference that helped in October may be in the way by December, because your work changed, or because Copilot did. Treat this page the way you treat a good colleague: a short feedback session now and then, a line added, a line removed. Ten minutes, not an afternoon. You evolve together, and so do the settings.