Jakob Nielsen's 10 general principles for interaction design. They are called "heuristics" because they are broad rules of thumb and not specific usability guidelines.
Anyone including non-designers can use this framework to analyse a product or service or analyse a piece of work for a potential client. You could even use this to review your own work as the tools and techniques I use leave little room for bias.
UX Review
A UX Review Template Anyone Can Use — UX Planet
Knowledge
How To Write Email Newsletters That People Actually Want To Read