Since userscript.org suddenly disappeared, a couple of years ago, and without a valid alternative on the horizon, I was creating (and maintaining) my little scripts only as Google Extensions (Shame on me).
In the last couple of weeks, I had the exigency of using one of my scripts for debugging on Safari and I took this chance to go through the use of User Scripts in different browsers.
The conversion is straightforward, you just need to add some config text at the top of your file, and it also gives you some handy features, for example, the possibility to add an updated URL where you can link directly your script from its remote repository (Pretty handy, isn't it?).

Installation on Chrome
  1. Download the user script.
  2. Open chrome://chrome/extensions/.
  3. Drag and drop the script file in the browser window.
Installation on other browsers
  1. You need an extension in order to use UserScripts in your browser, here are the most popular:

  2. Import your script or install it by clicking on its link.

If you are curious to give a look at some UserScripts I was working on lately, here we go: