I use a variety of tools and guides.
I always use the latest scholastic and professional style guides such as:
1) The Chicago Manual of Style (CMOS)
2) Modern Language Association Handbook
3) American Psychological Association (APA)
For fiction writing, I have found the 2019 book Dreyer’s English: An Utterly Correct Guide to Clarity and Style utterly invaluable. And it is a hilariously educational read.
For proper English, I rely primarily upon the Merriam-Webster and the Oxford dictionaries. However, some projects may use unconventional language or urban/slang vernaculars. In those cases, I have or will find the resource to ensure language speaks the truth of the project.
I have other tools and guides, but these are my most common reference works.