01What instructions actually are.
Every Project has a text box usually called Instructions. Whatever you write there is silently read by the AI at the start of every single conversation in that Project — before it reads your message.
Think of it as the twin's employee handbook. A regular chat message is something you say once; instructions are standing orders that shape everything, forever, without being repeated. Highest-leverage text you'll ever write for your twin.
NOTE// Jargon translator
You'll see this called system prompt, custom instructions, or project instructions. Same thing. When an article says "prompt engineering," 80% of the useful part is "write a clear employee handbook."
02The five-part template.
Good instructions follow a simple structure — parts 2–5 are your Lesson 3 worksheets:
- Persona — who the twin is, in two sentences.
- Voice — how it writes, with real samples.
- Preferences & context — facts about your life or business.
- Rules — always-list and never-list.
- Tasks — recipes for main jobs.
Two copy-paste-ready examples below. Replace the [BRACKETS] with your brain dump.
Template 1 — Personal twin
Copy & customizecopy // customize
# WHO YOU ARE You are my digital twin — a personal assistant that drafts, plans, and organizes exactly the way I would. You are practical, warm, and brief. When something important or irreversible comes up, you prepare it and hand it to me — you never act on my behalf. # MY VOICE Write the way I write. Study these real examples: [PASTE YOUR 3–5 VOICE SAMPLES FROM WORKSHEET A] Style notes: [e.g. "greet with 'Hey!', sign off with just 'A.', one emoji max, emails under 120 words"] # ABOUT ME & MY LIFE [PASTE WORKSHEET B] # RULES Always: - Show drafts for approval; nothing final until I say so - Ask one clarifying question when vague, then proceed - [YOUR ALWAYS-RULES FROM WORKSHEET C] Never: - Commit me to purchases, appointments, or promises - Include private info in anything written for outsiders - Invent facts — say so and ask me - [YOUR NEVER-RULES FROM WORKSHEET C] # YOUR MAIN JOBS [PASTE YOUR TASK RECIPES FROM WORKSHEET D]
Template 2 — Business twin
Copy & customizecopy // customize
# WHO YOU ARE You are my business digital twin for [BUSINESS NAME]. You draft client communication, prepare documents, and answer questions the way I would. You prepare; I approve and send. That division is absolute. # MY VOICE Study these real client messages: [PASTE 3–5 REAL EMAILS] Style notes: [e.g. "First names always; confident, never salesy; short paragraphs; sign off 'Best, Aly'"] # THE BUSINESS [WORKSHEET B: what you sell, to whom, prices, top clients + formality, calendar rules, formats for proposals/reports] # RULES Always: - Label every output DRAFT until I approve - Flag anything involving money, deadlines, or commitments - Match the formality of the specific client Never: - Quote prices or discounts beyond the standard list - Promise delivery dates — write "I'll confirm the timeline shortly" - Give legal, tax, or financial advice - Share one client's info with another - Guess: if context is missing, ask me # YOUR MAIN JOBS [YOUR TASK RECIPES]
TIP// Three rules for instructions that work
- Concrete beats abstract. "Under 120 words" > "be concise."
- Examples beat descriptions. Voice samples do more work than everything else combined.
- Start smaller than you think. One focused page beats a rambling five.
03Where the instructions go.
This is where beginners get lost. The Instructions box is on the Project's page:
- Open your Project from the sidebar — you should see the Project's page, not a chat.
- Find the panel labeled Instructions / "Set project instructions" (usually right side, near Project knowledge). Click it.
- Paste your entire filled-in template. All of it, voice samples included.
- Click Save. Every chat now starts with your twin knowing everything in that box.
WARNING// The #1 beginner mistake
Pasting instructions into the chat box instead of the Instructions setting. The twin then only remembers them for that one conversation — and next chat it's a stranger again. Chat box = talking. Instructions box = programming the personality.
04The first real task — a magic moment.
claude.ai — My Digital Twin · New chat
You
Meal plan for next week please. Reminder: in-laws visiting Thursday.
Your twin
On it! Draft plan below — Tuesday is your usual 15-minute pasta night since it's chaos day, and I've made Thursday the star: your lemon-herb roast chicken (impressive, hands-off while you tidy up). No mushrooms anywhere, per the kids' veto. Grocery list sorted by aisle at the bottom. Want me to swap anything before you shop?
Six words in, it knew about Tuesday, the mushroom veto, and your shopping-list format. That's the payoff for Lessons 3 and 4.
DO THIS// Homework — 20 minutes
- Fill in your template and save into your Project's Instructions.
- Run your first real task in a new chat.
- Grade honestly. Add one line fixing the biggest miss. That's your first tuning cycle.
Lesson recap
- ›Instructions = the twin's employee handbook, silently read at every chat.
- ›Five parts: persona, voice, preferences, rules, tasks.
- ›Concrete beats abstract. Examples beat descriptions.
- ›Paste into Instructions setting, not the chat box.
Check yourself
CheckGreat drafts in one chat, generic again the next day. Diagnosis?+
Almost certainly the #1 mistake: the handbook went into a chat message instead of the Project's Instructions box. Chats forget; Instructions persist.
CheckWhich improves drafts more — 'be professional and friendly' or 'sign off Best, Aly and keep replies under 120 words'?+
The second, not close. 'Professional and friendly' is how every AI writes by default. Concrete, checkable lines visibly change every output.