Start with the most recent provider
The most counterintuitive thing about hunting old medical records is how much of the work the current provider has already done for you. When a new patient walks into a primary-care office, the practice typically asks the prior provider to forward records — not always all of them, not always promptly, but often the most important pieces. The record you're looking for may already be sitting in a chart at a doctor's office two cities away from where the original event happened. The retention-rules companion explains the legal landscape; this step is about where the records tend to actually live in practice.
Ask the current primary-care doctor for a copy of the patient's complete chart — and pay attention to the word 'complete.' Not the after-visit summary. Not the printable health summary. The full designated record set under HIPAA, including the referral letters and prior-record forwards the office holds from earlier providers. Phrase the request in writing if you can; a written request triggers HIPAA's thirty-day clock and creates a paper trail you can point to if the office tells you it'll take a few months. We come back to the right language in Step 2.
A surprising amount of history surfaces from this single ask. Specialists send consultation letters back to the referring primary-care doctor by default — that's a record of what the specialist saw, often with their plan attached. Hospitals send discharge summaries to the patient's primary-care doctor as part of the standard transitions-of-care workflow. Imaging centers send formal reports to the ordering physician. The primary-care chart is therefore a thicker historical record than most patients realize; even visits to clinicians the patient has long since stopped seeing tend to leave a trace there.
If the current practice has been the patient's home for many years, this step alone may produce most of what you need. If the patient has switched primary-care doctors recently, repeat the same ask with the previous primary-care office — they almost certainly had records that the new office never asked for. Pediatric records often work this way too: the current pediatric or family-medicine practice usually has at least a summary of immunizations and major illnesses forwarded from the previous practice.