Assuming you're asking about a part of the site that's customizable, it's as simple as raising a new meta question with your suggested changes (or asking for suggestions) and reaching a consensus.
Many changes can be made instantly by a moderator, and the rest require staff intervention.
There are a few places in the Tour that can be changed by moderators:
- Top section ("English Language & Usage Stack Exchange is a question and answer site for linguists...")
- Example question (note: not visible at small widths, such as on mobile)
- "Ask about" bullets
- "Don't ask about" bullets
The Tour has always struck me as being a page for people who don't know anything about Stack Exchange. All of these sections should be kept brief and possibly link to meta posts where everything can be explained more fully.
Moderators can edit:
- The top of the main page, between the search bar and "Find out more about". If it looks like there's nothing there, that's because there isn't... yet.
- What topics can I ask about here? (which desperately needs more than the superficial edits I recently gave it)
Additionally, if there's a good reason to, staff can allow moderators to edit more Help pages. The downside is that these pages won't receive any of the updates that are supposed to be deployed across every site, such as updating screenshots or covering new features.
The Ask page
There are two places that can be edited here:
- The popup "Asking a good question" (you may need to try incognito if you don't see this)
- The box under "Step 1: Draft your question" (which is collapsed by default on mobile)
Both of these require staff to change. More info here: What site-specific changes can be made to the Ask Question page to help askers on that site write better questions?
Tags have wikis and excerpts that can be edited by anyone, usually through suggested edits. However, the wiki is so hard to find it might as well not exist and the excerpt isn't much better (I don't think it shows at all when you're tagging on mobile).
To make information about a specific tag more prominent, we can use tag warnings (aka tag tips). In the current iteration of the Ask page, these show up after you click "review question". (It also sometimes shows up when the post is being edited, though this is rarely the right time to be giving advice.)
This requires staff to implement.
Everything else you need to know about this can be found in my question Warn people of the rules for [Single-Word-Requests] before posting.