Play the game first! You don't have to devote hours upon hours playing a game to form a solid opinion on it (7-10 hours is more than enough). If you do it right a solid review doesn't actually take too much time to write.
Regardless of the type of game being reviewed, several topics about the game are sure to be covered. There will always be an introduction, five or more primary paragraphs, and a conclusion. Your review should include paragraphs that cover fun factor, control and gameplay, graphics, sound and replayability.
Writing a good review is all about maintaining balance. You want to provide the reader with essential details and insightful opinions without bogging them down with unnecessary details and useless musings.A typical word count for a finished review should be around 1,000 words.
Your review must be unique without grammatical and syntactical mistakes.