The setup almost nobody does
Here's the thing most people miss when they start using AI: every new conversation starts from zero. The AI doesn't know who you are, what you do, how you like to communicate, or any of the context that would make its output actually useful for your specific situation. You have to re-explain everything. Every time. That friction compounds into a significant amount of wasted time — and a lot of generic output that you spend time fixing to match your actual needs.
Custom instructions (Claude calls them "system prompts" or you can set them at the project level; ChatGPT has a "Custom Instructions" setting) solve this entirely. You write them once. They load into every conversation automatically. The AI already knows your business before you type the first word.
"The difference isn't subtle. A conversation that starts with full context produces fundamentally better output than one that starts from nothing."
What to include
A good custom instructions block covers five things:
- Who you are: Your role, your business, your industry, your location. Not your life story — the relevant context for the kind of work you'll be asking it to do.
- What you do: Your specific services, who you serve, your typical client, the problems you solve.
- Your tone: How you communicate. Direct? Warm? Technical? Casual? Australian English? No corporate speak? Give it a clear picture of your voice.
- What you always want: Practical suggestions over theory. Specific examples. Short responses unless you ask for long ones. Australian spelling. Whatever your consistent preferences are.
- What you never want: Filler phrases ("Certainly!", "Great question!"). Overly formal language. Generic advice that ignores your context. Bullet points when paragraphs work better. Whatever you've found yourself editing out every time.
The template
Here's a template structure you can adapt. This is for a trade or service business (more on AI use cases for trades) — modify for your own situation:
I run [business name], a [trade/service type] business in [suburb/city], [state]. I've been in the industry for [X] years. My services are [list]. My ideal clients are [describe]. What makes my business different is [1-2 genuine differentiators].
When I ask you to write anything, use direct, warm, Australian English. No corporate language, no buzzwords, no filler phrases. Write the way a knowledgeable professional would speak to a client — clear, confident, and real.
Always: give practical advice I can act on immediately. Be specific. If I ask for a prompt or template, make it specific to my context, not generic.
Never: use phrases like "Certainly!", "Great question!", "As an AI language model", or "I hope this helps." Don't pad responses. Don't hedge unnecessarily. Don't give me generic advice when you have my specific context available.
How to set it up in Claude
In Claude, the best approach is to use Projects. Create a project for your business, add your context document to it, and every conversation within that project starts with full context. You can also paste a system prompt at the start of any conversation. The Projects approach is better for ongoing work — you set it once and every future conversation in that project inherits it.
In the Claude desktop app (Cowork mode), you can set context at the workspace level so it's available across sessions — not just conversations.
How to set it up in ChatGPT
Go to Settings → Personalisation → Custom Instructions. There are two fields: "What would you like ChatGPT to know about you?" and "How would you like ChatGPT to respond?" Fill both. The first is your business context. The second is your tone and format preferences. These load into every new conversation automatically.
The difference it makes — before and after
Without custom instructions, a request like "write a follow-up email to a client I quoted last week" gets you a generic professional email that you'll spend 10 minutes rewriting to sound like you. With custom instructions, the same request gets you something that already knows your business name, your trade, your tone, and your typical client — and you spend 2 minutes making minor tweaks. You'll find the specific prompts to pair with this in the prompt library — from quote generators to suburb pages to client communications.
Multiply that difference across every request you make in a week. It compounds quickly.
Beyond basic custom instructions, build a separate "business knowledge base" document — a comprehensive 1-2 page document covering your full service list, pricing structure, service areas, common FAQs, typical job types, and anything else that's relevant context. Paste this into conversations where you need deep business-specific output. It's the difference between AI that knows your industry and AI that knows your specific business.
Keep it updated
Custom instructions aren't set-and-forget forever. Review them every few months. Did you add a service? Change your target client? Move to a new area? Your context document should reflect your current reality — not who you were when you first set it up. 10 minutes every quarter is all it takes.
Use AI to write them
One of the better prompts in the free download pack is a meta-prompt for generating custom instructions — you describe your business in rough terms, and the AI structures it into a proper custom instructions block. If you're not sure how to write yours, start there. More prompts for every aspect of running a small business with AI are here.
The prompt to build your custom instructions
The free prompt pack includes the exact prompt to generate your custom instructions block from a rough description of your business. Takes about 5 minutes to set up properly.