Simple explanation
This lesson is the shortest in the entire challenge. But it might be the most important one to memorise. Every experienced Claude Code builder — developer or not — follows some version of these five rules. They are not complicated. They are not technical. They are just habits that prevent the most common mistakes. Write them down. Stick them on your wall. Add them to your CLAUDE.md. --- Golden Rule 1 — Always review before you accept. Every time Claude Code makes a change — look at it before you say it is fine. Claude Code shows you a diff — a list of exactly what it changed. Green lines were added. Red lines were removed. You do not need to understand the code. You need to check: Did it change only what I asked? Did it remove anything that looks important? Does the number of changes feel right for what I asked? If you asked it to change one button colour and it changed 47 lines — something is wrong. Do not accept. Ask what it changed and why. Reviewing diffs takes 30 seconds. Recovering from an unreviewed mistake takes hours. --- Golden Rule 2 — Use /compact at 70% context — not 90%. You learned this in Bonus 2. The rule is simple: when your session is 70% full — do not wait. Type /compact with specific instructions about what to keep. Do not wait until 90%. By then the damage is already happening. 70% is your trigger. --- Golden Rule 3 — Be specific. Always WHAT + WHERE + HOW + VERIFY. Every prompt should answer four questions: WHAT — what exactly do you want? WHERE — which file or section? HOW — how should it look or work? VERIFY — how will you know it worked? Weak prompt: "Fix the button" Strong prompt using all four: WHAT: Change the button label WHERE: On the homepage hero section HOW: From "Join now" to "Start for free" VERIFY: I will check by opening the site and reading the button text Full version: "On the homepage hero section change the button label from 'Join now' to 'Start for free'. I will verify by checking the live site." That one prompt format eliminates 80% of wrong results. --- Golden Rule 4 — Plan Mode before anything complex. You know this from Days 3 and 17. The rule: if a task touches more than one file or has more than two steps — turn on Plan Mode first. Do not skip this to save 2 minutes. The plan review catches problems before they happen. The time you save skipping Plan Mode is always less than the time you lose recovering from the mistake. If in doubt — plan first. --- Golden Rule 5 — CLAUDE.md is your single source of truth. Everything important about your project should be in CLAUDE.md. Your colours. Your fonts. Your rules. Your no-go zones. Your current goal. If you find yourself repeating an instruction to Claude Code more than twice — that instruction belongs in CLAUDE.md permanently. Before every session — open CLAUDE.md and check the Current Goal section is updated. Your CLAUDE.md is the one place where your project memory lives. Keep it current. Keep it specific. Trust it.
What to do
Add the 5 Golden Rules as a section to your CLAUDE.md file. Title the section: "Session Rules — Follow These Every Time" Write each rule in your own words — so they feel natural to you. Start your next session and consciously follow all five. Notice which ones you were already doing and which ones feel new. You can use the copy-paste prompt on this page to do all of this in one step.
Copy-paste prompt
Add a new section to my CLAUDE.md file called 'Session Rules — Follow These Every Time'. Include these 5 Golden Rules written in simple plain English: 1. Always review the diff before accepting any change. 2. Use /compact at 70% context with specific instructions about what to keep. 3. Every prompt needs WHAT + WHERE + HOW + VERIFY. 4. Use Plan Mode before any task that touches more than one file. 5. Everything important lives in CLAUDE.md — keep it updated before every session.
Course note
Key takeaway
1 — Always review the diff before accepting any change. 2 — Use /compact at 70% context — not 90%. 3 — Every prompt needs WHAT + WHERE + HOW + VERIFY. 4 — Plan Mode before anything that touches more than one file. 5 — Everything important lives in CLAUDE.md — keep it updated.