Your review will help the editor decide whether or not to publish the article. It will also aid the author and allow them to improve their manuscript. Giving your overall opinion and general observations of the article is essential. Your comments should be courteous and constructive, and should not include any ad hominem remarks or personal details including your name.
Providing insight into any deficiencies is important. You should explain and support your judgement so that both editors and authors are able to fully understand the reasoning behind your comments. You should indicate whether your comments are your own opinion or are reflected by the data and evidence.
When you make a recommendation, it is worth considering the categories the editor will likely use for classifying the article:
The editor ultimately decides whether to accept or reject the article. The editor will weigh all views and may call for another opinion or ask the author for a revised paper before making a decision.