Your best clients are the brief
Ask an agency owner to describe the ideal client and you get a sector and a headcount. Ask which five clients they would clone and you get a better answer, because that list carries things nobody writes down: how those companies buy, how they decide, what kind of hiring they do. A lookalike search uses the companies themselves as the brief.
The risk is that it copies the wrong thing. Give it five clients and it will find whatever they share, whether or not that is the reason they are good clients. So the play has a checkpoint before any expansion: the agent states what it thinks the seeds have in common, and you correct it.
What you get back
First the profile, in plain words: what the seeds share and the signs that would prove a fit. Then a table of companies with name, website, size, sector and location, the seed and the source that surfaced each one, the reason it was judged similar, and a tier. Tier A was checked against the company's own site, with the evidence attached. Tier B fits on the record. Tier C is possible. Contacts appear only if you asked for them.
Variations worth knowing
Tighten or loosen the similarity. One source grades its matches from near-identical to broadly similar. Start tight, and widen when the near-identical pool runs out.
Split a mixed seed set. If your best clients fall into two distinct types, run each group on its own. A mixed set produces a blurred profile and a list that resembles neither.
Add timing afterwards. A lookalike is a fit, not a reason to call today. To be told when one of these companies starts hiring, use know when a target account opens a role in your discipline. For a whole market and its size, use build the target account list for a recruitment desk.
Where this goes wrong
A seed resolves to the wrong company. Shared web addresses and common names match the wrong business. The play shows each resolved seed before it expands, which is the cheap moment to catch it.
The pattern is an accident. Seeds that share a trait by coincidence produce a list built on that trait. The read-back step exists for this, and it only works if you answer it properly.
Lookalikes are often rivals. Decide before the run whether a client's competitor is a lead or a conflict, and say so.
Thin records at small companies. Small and young businesses carry little data, so similarity is weaker there and more of them land in tier C. Treat that tier as a reserve, not a call list.
