Most AI assistants let you set instructions that apply to every conversation. Depending on the tool, they're called custom instructions, personalisation, project instructions or a system prompt. Used well, they're one of the biggest quality upgrades you can make.
What they are
A system prompt is background guidance the AI reads before your message. It sets the role, tone, format and rules. Custom instructions are the consumer version: a box where you describe yourself and how you'd like responses.
What to put in them
- About you: your job, expertise level, industry and location (for spelling, currency and units)
- Preferences: concise vs detailed, bullet points vs prose, tone
- Defaults: "Use British English", "Show code in Python unless I say otherwise"
- Things to avoid: filler phrases, unnecessary disclaimers, emojis
An example
I'm a marketing manager at a small B2B software company.
I know marketing well but I'm not technical.
Be concise and practical. Use short paragraphs and bullet points.
Ask a clarifying question if my request is ambiguous.
Don't use the words "delve", "unlock" or "elevate".Projects and custom assistants
Many tools let you create separate workspaces with their own instructions and reference files: one for your newsletter, one for coding, one for customer support. This keeps each context focused.
Tips
- Keep instructions short and specific; long, contradictory lists get ignored.
- Review them every few weeks and remove what isn't helping.
- Don't put passwords or confidential data in instructions.
- Test: ask the same question with and without instructions to see the difference.