Are you aware of, and able to follow the ethical guidelines for peer reviewers? 

Do you understand the type of peer review used by the journal?

Are you aware of how to submit your review? For most journals, you will complete a form online which may consist of structured questions and/or free text boxes. But in some cases, you may need to email your report to the editor.

Do you have any conflicts of interest? If so, make the editor aware immediately.

Can you complete the review in the allotted time? If you may struggle to meet the deadline, please let the editor know, so they can inform the author.