I do not know much about the writing conventions specifically for APA but I think these would be relevant for any kind of academic writing, you should not use slang or informal language (words like cool, awesome, AF or abbreviations like ASAP, TGIF) while writing an academic paper. Avoid beginning a sentence with a number, try to use a modifier like “About, Approximately” before doing so. Use qualifiers sparingly, frequent use of words like ‘very, for example, always, usually’ can make the writing seem too informal and lazily done. Also try to limit the use of first person pronouns as much as possible and the overall language for the paper should not appear to have a biased, discriminatory or sexist overtone.