Begin with the business problem, not a feature list. Which people will use the system, how many times a day, and what happens today? An experienced team who understands the goal will suggest a simpler way to reach it; a team that receives only a list of screens prices exactly what you asked for.
Define what is included as user stories or scenarios: who does what, and what happens next. Every bit as useful, state explicitly what is out of scope. A written out-of-scope list saves more argument during acceptance than almost anything else hire developers in russia the document. Mark too which decisions are settled and which are still open — estimators price uncertainty, and concealing the open questions helps nobody.
Write down the hard constraints. The list covers the platforms and services involved, existing databases and their quality, regulatory obligations, expected load, which devices matter and any technology you are committed to. Where a date is genuinely fixed, say what depends on it: a good team can often cut the right scope to hit it, but not if the date is a secret.
Define what completion means for the important items. Acceptance criteria need not use any formal notation: a short list setting out the expected behaviour is enough. This single habit compresses acceptance testing dramatically and removes the most common source of disputes.
Finally, ask for a industry specific software development format. Request a task-level breakdown, the assumptions behind each number, whatever the team considers risky and an optimistic and a pessimistic figure. Take a broad range as information, not evasion: it usually points to the part of the brief that needs work. Then tighten that section and ask for a new estimate — the next version is much more reliable.