A requirements doc is a translation, not the original.

The document a client hands you is their daily work translated into "software language". Translation always loses something, and what it loses is usually the expensive part.

So don't rush to build what the doc says. Sit beside them and watch how the work actually happens: which spreadsheet opens first, why one column gets copied by hand, what that daily afternoon phone call is really confirming.

Draw the diagram they never drew themselves.

Sketch the flow you observed, then show it to them. Most of the time they will say "close, but this bit is wrong" — and that "wrong" is the biggest thing you take away from the week.

The gap between the real flow and the described flow is exactly where software creates value. Miss it, and all you can build is a faster spreadsheet.

Resist quoting a timeline.

After one week you do not understand the business well enough to estimate anything. A date given now is a date repaid later in overtime.

The honest version: this week I map the flow; next week we pick the most painful step together and do that one first. It sounds slow. It is the only start that needs no rework.