I've been editing some titles with the plan to come here to ask this same question so glad so many beat me to it!
My current understanding is we are collaboratively curating great answers to the list of all the relevant questions related WordPress. The idea being that if someone has a reasonably question about WordPress that ideally we should a somewhat authoritative and complete answer here. Is everyone in agreement with this?
With that in mind here are my current evolving thoughts about titles. I think:
We should edit the (typically vague) titles after we've identified what the actual question really is.
We should edit titles to be what thing we think someone will most likely search via Google or other search engines when they have the same or a similar problem.
We should definitely end with a question mark except in the infrequent cases where it should obviously not be the case.
Questions should include the word "WordPress" because that is how they will be naturally asked and thus will be more recognized by users scanning the site and will more likely match when someone searches for same via Google, etc.
We should proper case most words in the title except for words like "to", "the", "and", "with", "if", etc. This will make them stand out as titles and this is a grammar best practice anyway. Of course we should probably come up with our own rules for this.
Now I'm on the fence with "How do I.." as a prefix. Cons are that it makes the titles longer and make it harder to differentiate a list of questions on the page simply by scanning them. Pros to include "How do I..." are that it would more likely match a Google search where someone searches "How do I xxx." Not sure where to go with this...
As a side I think this site will be more successful with less questions that are better managed and maintained than a bunch of one-of obscure questions with two or three answers each a couple lines long.