Somewhere between "never type anything into that thing" and "paste in whatever, it's fine" is a sane middle, the same middle you already navigate with email, texting, and every app on your phone. You don't need paranoia. You need a few defaults you never have to rethink.
The five rules
1. Never share what can unlock money or identity
Social Security numbers, full account or card numbers, passwords, PINs, security-question answers, photos of IDs or passports. Not because an AI chat is uniquely dangerous, because this class of information should never sit in any chat log, anywhere, period. The habit is the protection.
2. Blur the details that don't change the answer
Here's the liberating part: AI doesn't need real identifiers to help you. "My daughter, age 7, at a school in a big city" gets you the same advice as her name and the school's. "A company doing about $2M in revenue" works as well as the company's name. Swap specifics for shapes and you lose nothing.
3. Other people's information isn't yours to paste
The clearest rule and the most broken one. Your friend's medical situation, a client's financials, your company's internal documents, that email someone sent you in confidence. If work gives you an approved AI tool, use it for work things; if not, ask what's allowed before pasting anything internal. "I anonymized it" is the standard, actually anonymize it.
4. Spend two minutes on settings
Every major AI tool has a version of "don't use my conversations for training" and a way to delete history. Find them once: it's in Settings under Data Controls (ChatGPT), Privacy (Claude), or Activity (Gemini). Turn off training use if the option exists, know where delete lives, and move on with your life. Two minutes, done forever.
5. Assume the chat could someday be seen
Not because it will be, because it's the right calibration. The mental test: would I put this in an email? Emails get forwarded, subpoenaed, breached, and screenshotted, and we all use email constantly anyway. Same posture here: useful for nearly everything, trusted with the crown jewels never.
What this leaves you free to do
Everything that matters, honestly. Meal plans, hard emails, business plans, career strategy, trip logistics, homework help, the negotiation rehearsal, the messy 11pm idea, none of it requires a single piece of information from the never-share list. The point of rules isn't restriction. It's that once the defaults are set, you stop spending attention on the question.
Privacy isn't the opposite of using new tools. It's what lets you use them without a second thought, and the second thoughts were the real cost.