Links to useful features like re621 and Tag Visualizer should be placed somewhere prominent.

In particular re621's Quick Blacklist is a good default.
(However, there is also the problem that the script is not well understood (users like me) do not know how to download it).

drag007 said:
Links to useful features like re621 and Tag Visualizer should be placed somewhere prominent.

There's e621:tools which lists a lot of helpful tools, though the list isn't very well maintained, some stuff is broken and other newer stuff is missing.

drag007 said:
(However, there is also the problem that the script is not well understood (users like me) do not know how to download it).

First you need to install a browser extension like Tampermonkey or Greasemonkey . After installing the extension, clicking a link to a userscript (such as the first one under the "Releases" heading here) will open a page to install the userscript (screenshot)

faucet said:
There's e621:tools which lists a lot of helpful tools, though the list isn't very well maintained, some stuff is broken and other newer stuff is missing.

It seems that the e621:index link itself is hard to find. Tentatively, there seems to be a link back from the Tagging Checklist in the help and the rules at the bottom of the screen...Either way I can't find a route from the page header to the main entrance.

drag007 said:
Links to useful features like re621 and Tag Visualizer should be placed somewhere prominent.

They are on my profile page. https://e621.net/users/bitWolfy
Since these are not official tools, I don't think it's appropriate to pin them on the forums or something like that.

drag007 said:
In particular re621's Quick Blacklist is a good default.
(However, there is also the problem that the script is not well understood (users like me) do not know how to download it).

First, go here and click "Install". That will install the script manager that will be used to actually run the script.
Then, go here, click "Install", and follow instructions on the screen. That will set up the script.
After that, just reload the page on e621, and you are good to go.

faucet said:
First you need to install a browser extension like Tampermonkey or Greasemonkey.

Greasemonkey is not officially supported due to a myriad of issues I had trying to get re621 to run on it.
Use something more modern, like Tampermonkey or ViolentMonkey.