The standard advice is to ask every customer for a review. It is close to right and the gap matters.
An untargeted blast reaches the delighted, the indifferent, and the annoyed at the same moment. The indifferent ignore it. The other two both respond, because strong feeling is what makes someone act. You have built a machine that harvests your best and worst experiences at the same rate.
Ask, but ask in the right order
Find out how the job went before you point anyone at a public review form. A single question by text does it: how did we do, one to five.
Four or five
Send the review link. This person is glad you asked and the request will not annoy them.
Three or below
A human calls them. Something went wrong and you now have a chance to fix it while it is still fixable.
Routing unhappy customers to a private conversation instead of a public form is fine. Blocking them from leaving a public review is not, and platforms treat it as a policy violation. The difference is whether the review link still works if they go looking for it. It should.
A low rating is not the disaster
A profile with nothing but five stars reads as fake to most people, and shoppers routinely go straight to the negative ones to see how a company behaves under pressure. A calm, specific reply to a bad review does more for a hesitant buyer than another perfect score.
What actually hurts is a bad review with no reply. That reads as a company that either did not notice or did not care.
Timing beats volume
Ask while the job is still fresh, the same day where you can. A request that arrives two weeks later competes with everything that has happened since, and loses.
If your website displays a star rating or a review count, pull it live rather than typing it in. Hardcoded numbers drift, and a figure on your site that disagrees with your public profile is a problem you created for yourself.