I've written this short guide to good tagging based on my experience setting up tags for this site.
Eating Patterns
If your question only makes sense in the context of a habitual eating pattern (a "diet"), make sure to include the appropriate tag for the kind of eating pattern that you are following.
For example, questions like "Can I eat XYZ product?" or "What can I use to replace XYZ ingredient?" can only be answered when it's clear what kind of eating pattern is being followed, so it is essential to identify that right away.
Nutrition
Questions that approach food and human health from a nutritional science perspective (an understanding of component nutrients) should aim to use the most specific nutrition tags available.
Or nutrition if no specific tag is available.
Food Groups
If you're looking for alternatives to traditional food groups or ingredients, use one of these tags:
There are also tags for many foods and food groups that are of particular interest to vegans and vegetarians.
Recipe Request
If you're looking for specific guidance on how to combine ingredients, especially if you're new to vegan and vegetarian cooking, use recipe-request to learn about replacements for nearly any traditional or cultural dish.