Professional editors and proofreaders use a style guide. If you went to university and had to present your references in a particular manner (all you educators out there APA v6…), you used a style guide.
In journalism, AP is common; in academia, many different style guides depending on your specific area. In fiction, many authors don’t know they exist.
A style guide is a guide to how to set out your manuscript. It outlines how to format headings, paragraphs, lists, captions; you name it. The Chicago Manual of Style is frequently used for USA fiction books, whilst The Australian Style Guide is used in Australia. Guides are updated frequently and often have a free trial period for the online version.
A style sheet, is a customized sheet specific to your manuscript. It should contain the spelling of any of your character names, locations (particularly made-up locations), author-constructed languages etc. If it’s 500 pages long, you’ve got too much detail. Provide your style sheet to your copy editor and proofreader. Some editors will include the creation of a style sheet in the cost of your job—some charge you extra. You can create your own.
If you are looking after your editing and proofreading (not recommended, but not everyone has a budget for editing), then create your own and keep it beside you as you edit. You can also add a custom dictionary to most word-processing software packages and add your created names, locations, units of time, etc.