I have started to assist my clients in printing business cards w/ short URLs that direct customers to their own review pages. Vista Print is a very inexpensive and reliable service for these. Go to some of the short URLs ( for example -http://bit.ly/RWDGoog ) in these business cards and see.
For Google Reviews, customers must also have a Google account in order to write a review. Customers need to post the reviews themselves, through their Google+ accounts. Customers can leave ratings without actually writing a review. The rating is just the "stars" without the text of a review. At least in terms of rankings, the number of reviews you have seems to matter more than the quality of those reviews.
Best-practices for requesting reviews - Ask everyone for a review, not just your diehard, happiest customers. Point out as often as possible that you'd like your customers' honest feedback. Don't incentivize - Not only is it against the rules, but makes you look as though you're desperate. Your customers care, not all of them, but that's OK. Many will write a review if you ask and especially if you give them basic instructions as to how.
Place a line on your email signature that guides people for reviews. Where have you seen this before???