Always follow the abstract guidelines by the journal you are wishing to publish in. That being said, these are some general requirements for writing abstracts:
What are the keywords for? They are used for indexing and abstracting of your articles, i.e., they help people searching in databases to be able to find your article.
What should I use for keywords? Basically you want to use words that collectively describe your research. They should summarize what your article is about. Look at some publications in your research area and see how they write their keywords. Really think about what the keywords in that particular research are describing or trying to focus on.
What is the format for keywords? Always follow the journal guidelines that you are publishing in. Most likely they will have specifics. Following APA 7th edition guidelines, the phrase Keywords is to be in italics with a colon, followed by the keywords or phrases separated by commas. After the last keyword, no punctuation is used.
So if I were writing keywords for this research guide I might use:
Keywords: library research guides, LibGuides, APA 7th edition, citation styles
Vollbehr, N. K., Hoenders, H. J. R., Bartels‐Velthuis, A. A., Nauta, M. H., Castelein, S., Schroevers, M. J., Stant, A.D., de Jong, P.J., & Ostafin, B. D. (2020). A mindful yoga intervention for young women with major depressive disorder: Design and baseline sample characteristics of a randomized controlled trial. International Journal of Methods in Psychiatric Research, 29, Article e1820. doi:http://dx.doi.org/10.1002/mpr.1820
Reddy-Best, K.L. & Choi, E. (2020). "Male hair cannot extend below plane of the shoulder" and "no cross dressing": critical queer analysis of high school dress codes in the United States. Journal of Homosexuality, 67(9):1290-1340. https://doi.org/10.1080/00918369.2019.1585730
In this study, we questioned how high school dress codes outlined in official handbooks were written or presented in regard to the gender binary, either/or perspective. We critically analyzed how or if they allowed for flexibility in expression of gender and sexual identity and if they supported, encouraged, or affirmed a variety of expressions, in particular transgender and gender non-conforming expressions, throughout the text or images. The content analysis method was used to analyze 735 handbooks from the 2016 to 2017 school year. Three themes emerged from the data: (1) support of fluid gender expression, yet not overt support; (2) passive marginalization of gender non-conforming or transgender identities or expressions; and (3) active marginalization of gender non-conforming or transgender identities or expressions. The “LGBTQ+ Dress Code Analysis Tool” was developed for policy makers to use to analyze their dress codes.
Keywords: Dress code, gender, high school, LGBTQ+, queer, sexuality