Look at the samples provided. Ask questions if you run across anything which does not fit APA rules. Using incorrect margins. APA uses 1 inch margins on all sides. The bottom margin may be adjusted if needed, for example to avoid putting a heading on the last line of the page or to avoid putting the last few words of a paragraph at the top of the next page.
Page headers go inside the top margin.
Using an author's first name or using gender specific pronouns. APA requires nonsexist language and references at all times. Proof your work carefully. There is no reason to ever identify the gender of a researcher or author. Formatting the title page incorrectly.