Small steps, and test every time

The most common mistake: asking for the whole project in one go. The AI then hands back hundreds of lines, something doesn't work, and neither you nor it knows where to look. The method that works is the opposite: one small step, one test, then the next.

Start with the minimal version

First ask for the simplest version that works. For the flatmates' tool: "A page where I enter two expenses and the total appears. Nothing else for now." Once that works, add one feature: the names, then the who-owes-what calculation, then the phone layout.

Test after every change

• Really try it: click every button, enter normal values, then odd ones (zero, a negative number, an empty field).
• Check with a case whose answer you know: if Léa paid 30 euros and Tom 10, each should have paid 20, so Tom owes Léa 10 euros. If the tool says otherwise, it's wrong, however nice it looks.
• One change at a time: if you change three things and it breaks, you won't know which one did it.

Keep versions

Before each new step, keep a copy of the version that works: a "v1", "v2"… folder, or a version-tracking tool like Git, which the AI can teach you to use. If the next step goes wrong, you go back in ten seconds instead of fixing everything.

Understand the basics

After each step, ask: "Explain in three sentences what you changed, and why." You don't need to understand everything, but you should know which part does what.