Suppose I want to search for postings of a known member John Doe under the tag Calculus. What steps do I take?
Similarly: How do I search for responses of user X to questions which have tag Y?
You can also go to the users profile and find the tags tab: https://math.stackexchange.com/users/current?tab=tags Then click on the tag which you are interested in.
When you do this, you will see what the syntax is. For example, when searching for your post in calculus tag you would use:
user:29038 [calculus] https://math.stackexchange.com/search?q=user:29038+[calculus]