Most businesses ask for reviews in a burst, get a handful, then stop. The ones with hundreds of reviews are not asking harder. They are asking every single time, as part of how a job ends.
Ask at the moment of relief
The best time is immediately after the problem is solved and the customer is visibly pleased. Not a week later by email, when the feeling has faded and your message is one of forty unread.
Make it one tap
Every extra step loses people. A short link sent by text, going straight to the review box, converts far better than "search for us on Google and leave a review". Google provides this link directly from your profile.
Have the person who did the work ask
A request from the technician who just fixed the problem lands very differently from one sent by an office nobody met.
Never offer anything for it
Incentivised reviews violate Google policy and can get your listing suspended. They also read as bought, which undoes the credibility you were buying.
Answer every one
Including the good ones, briefly. It signals an active business, and it means when you do reply to a critical review it does not look defensive.