Write the brief you wish you had been given
A short habit that has saved me more rework than any process: before starting, write the brief back in my own words and send it to whoever asked.
Before starting anything that will take more than a couple of days, I write the brief back in my own words, in under two hundred words, and send it to the person who asked for it.
It covers four things: what problem we are solving, who has it, what I am going to do, and what I am explicitly not going to do.
The reply is where the value is. Roughly a third of the time it comes back with a correction that would otherwise have surfaced in week three, when it would have cost a fortnight.
The rest of the time it comes back with a yes, and now there is a written record of what we agreed. That record settles the conversation, six weeks later, about whether something was in scope.
It takes fifteen minutes. I have never regretted the fifteen minutes.