Getting good service reviews starts with the process inside the dealership. Service staff has to be trained to ask about the customer's experience before they leave the lot. If they say anything that's not stellar, bring them back around and try to rectify any complaints. Give them a card to contact the GM, Service Director or some other outlet they can work with. If they say they had a great experience, give them a card directing them to leave a review. Have the staff member sign the card and let them know how much they appreciate them. You will be surprised how much a personalized touch helps increase the number of reviews you get.
Send an email to your service customers asking for the reviews. Like Alex says, this will increase the level of service because the service advisors now know their work may be graded.
One thing to watch for - look at the number of bounced emails you get when contacting service customers via email. You may get service advisors that will intentionally mis-type an email address so the review email never gets sent to that customer and they will never be graded. You can catch this by building a report per service advisor along with the number of bounced emails they get.
Hope this helps.
-Carl
