On the main site (also on meta), there is a sidebar for 'hot meta posts'. What are the criteria for a post to be shown on this sidebar, given that only a few questions are listed?
Hot meta posts are the posts which can be found in (the corresponding section of) the community bulletin. The main criteria for selection can be briefly summarized as: The question is tagged discussion, it has score at least $+3$ and it is at most 14 days old. There are also some further details, you can find the complete explanation in the corresponding FAQ post on Meta Stack Exchange: What criteria are used to select the links that appear in the community bulletin sidebar block?
I will add that since August 2020, it is shown in the revisions history whether a post became a "hot meta post". Another feature added at the same time was that they can be manually removed by moderators. (This is probably going to be used only in rather rare cases. As far as I can tell, moderators of this site haven't used this feature so far. For comparison, this happend twice on MathOverflow Meta and 9 times on Stack Overflow Meta.) See: Hot Meta Posts: Allow for removal by moderators, and thoughts about future improvements and August 2020 entry in Recent feature changes to Stack Exchange.
It might be worth mentioning that this is completely different from the hot network questions (HNQ) - they come from the main site (not from meta) and they are displayed in the sidebar (not in the community bulletin). See also: Hot Network Questions. How are they selected? (on this meta) and What are the criteria for questions to be selected for Hot Network Questions? (on Meta Stack Exchange).
Criteria for a post to be a 'hot meta post':
- Question should be tagged discussion
- Question should be present Math Meta StackExchange and not MathStackExchange
- Net score or upvotes minus downvotes $\geq3$
- Question should not be older than $14$ days
- Not tagged with any moderator status tag
Other special points:
Remember it is not necessary that every good post is a hot meta post. The converse is mostly true but not the original statement. It is possible that you have posted a good post but it didn't turn up as hot meta post. Don't sweat it.
"All hot meta post are excellent that is why they get many upvote." No this statement is not always true. Mostly hot meta post get a good amount of upvotes because hot meta post are very much observable and therefore catch "non frequent meta users'" eyes, so they visit it and upvote.
Remember after a post becomes a hot meta post even if its net score drops to < 3, it might remain in hot meta list for some time.
If you click on the time line option
you will be able to see when it became a hot meta post
If 3 people with delete vote privileges vote to delete the question, then it will be removed from the hot meta post list.
Mods also have the power to remove a post from Hot Meta Post list
Maybe your question soon also might be a Hot Meta post soon.