Decide what kind of number you want
Before anything else: a local number, a toll-free number, or the number you already have. The options for getting one range from a second mobile line through virtual numbers to full phone platforms, and they differ in price shape (per user or flat), in what they need from you to verify your identity, and in what they do for emergency calls.
How to get a business phone number compares eight option types with real team pricing. For the local-versus-toll-free question specifically, see local vs toll-free.
Pick the area code for the area you serve
For a local business the area code is a small signal that you are nearby. It is not always obvious which one to choose: many regions have overlay codes, a service area can straddle two codes, and a second location raises the question of a second number.
Which area code should your business phone number use? works through overlays, adjacent markets, multiple locations and what to check before you buy.
One main number, or a line for everyone
A single main number that routes to the right person keeps the business reachable when people change roles or leave. Direct numbers per employee give customers a straight line to their contact, but each one is another number to manage, and one to recover when somebody leaves. The third arrangement is a hybrid: a main number, plus direct lines only for the few people customers genuinely need to reach directly.
One business phone number vs individual numbers compares the three arrangements, including texting and offboarding.
If you already have a number, bring it
An existing business number can usually be ported, and the old line keeps carrying calls while the transfer runs. The one rule that matters most is not to cancel the old service before the port completes.
Porting your existing number covers the rules and why ports get rejected; how long does it take to port a phone number? gives the timelines by number type and country.
Write the menu
The greeting is the only part of the setup every caller experiences. Short, built around what callers ring about, with the option named before the key to press. Most small businesses need two to four options.
Phone menu scripts for small business has copy-ready scripts for six kinds of business, plus after-hours and urgent wording and a way to test them. Designing a phone menu people do not hate covers the principles.
Choose how each option rings
Ring everyone at once when the answer is "whoever is free". Ring in order when there is a real first choice with a backup. A call queue, where callers wait in line for the next available agent, is a different tool built for teams of interchangeable agents.
Call queue vs ring group vs auto attendant explains what each does when everybody is busy and which small-team scenarios need which.
Check you can take the calls you get
"How many lines do we need?" hides several different quantities: public numbers, people, devices and calls in progress at the same moment. The last one is the one that decides whether a caller gets through at your busiest hour.
How many phone lines does your small business need? is a worksheet for sizing it, with questions to ask any vendor and a test to run before you switch over.
Last, decide what happens after hours
Outside opening hours callers should hear something that tells them what will happen: a voicemail with a promised call-back time, or a route through to whoever is on call if your late calls are emergencies. Missed calls and after hours covers what unanswered calls cost and the options for covering them, including building an on-call plan for a small trade team.
Further reading
Longer research pieces on this topic, each with its own source list and a downloadable PDF.