Anywhere between 1 and 4+ keywords will usually be optimised to achieve 1st Page Google rankings. The exact number depends on the average monthly searches for each keyword and their relative online competition.
This is why having 4 keywords instead of 1 doesn’t automatically mean you’re getting 4x as much value…
Client ‘A’ may get 4 keywords with an average monthly search volume of 2,000 people.
Client ‘B’ may get only 1 keyword attracting a monthly online search of 8,000 people.
…Both result in the same traffic increase for the client.
Likewise, just because a keyword attracts a large monthly search, it doesn’t automatically mean it’s worth pursuing for SEO. We sometimes conclude that the money and time required to achieve 1st page ranking would be better spent on getting several keywords with less traffic instead. This is usually the case with smaller companies.
In all circumstances though we consult you throughout the entire process.
In short, deciding the keywords to optimise is complex. We’re guided by you and what products / services you’re marketing, but ultimately we choose the keywords and present these recommendations to you for approval.