Have the Right Product Knowledge
One of the most horrible reviewing mistakes I've seen on the part of many reviewers is that they don't care to test it out or perform some research about the products they review on their websites. To really build and maintain credibility with your target audience, you must ensure you have the right knowledge of the product you want to review.
The better your experience is with the product to be reviewed, the more trusted your review will be. Thus, try to have the right product knowledge, use, understand the benefits and other necessary information readers would need to know before they start spending their hard-earned money.
State the Pros and Cons
While writing a review for any product, don't be narrow-minded but consider stating, in clear terms, what the deficiencies are and the benefits readers will stand to gain by purchasing the product.
Spell out the negatives and positives clearly in a tabular form for analogy purpose.
Give Product Samples
In your review, give samples of the products you've used or tested out so far and state if such items are worth purchasing.
Product Review Plugin for WordPress
WordPress site owners can download and install the product review plugin on their websites. This plugin will help them turn the posts on their blogs into detailed and useful reviews with pros and cons, user reviews, user ratings, rich snippets, and affiliate links.