Founders treat the domain as a naming exercise and discover later it was a diligence exercise. The name you pick will be spoken in every pitch, printed in every footer and typed by every customer. An hour of checks before committing saves the two classic disasters: building on a name you can't keep, and inheriting a domain someone else already ruined.
Check registration status first
The canonical source for whether a name is taken is not your registrar's search box - which mixes availability with upsells - but the registry data itself. ICANN Lookup (lookup.icann.org) shows a domain's registration status, registrar, and registration and expiry dates in one query. A name that resolves to a parked "for sale" page is registered even if nothing is built on it; the lookup tells you the registrar and when it lapses. Who actually owns it is often hidden: registration data is frequently redacted under privacy rules or masked by proxy services, so treat the registrant fields as a lead, not an answer.
Check the history, not just the status
An available or cheap domain may have had a past life. Expired domains carry their history with them: old backlinks, old content, sometimes old spam. Before buying a previously registered name, look at what it used to be - if it hosted something you'd be embarrassed to be confused with, walk away or price in the cleanup. Your future customers and search engines both have memories.
Say it, type it, mistype it
Three practical tests before committing. Say the name out loud to someone and ask them to spell it; if they can't, every podcast and word-of-mouth mention leaks traffic. Type it fast; letter pairs that merge (two words sharing a letter) or that spell an unintended word are permanent. And check the obvious mistypes: if a lookalike domain exists, someone may someday register it to catch your customers, so grab the cheap variants early while they are still cheap.
Treat renewal as infrastructure
More companies lose domains to expiry than to disputes. Turn on auto-renew, keep the registrant contact email alive (renewal notices go there), and add a registrar lock so the name can't be transferred without your approval. If the domain is central to the business, register it for multiple years - the cost is trivial next to the risk of a lapsed registration being scooped.
The goal isn't a perfect name; those are gone or expensive. The goal is a name you can say, keep and defend, bought with open eyes about who held it before you.