Some applications look like simple image files (total = 1) living in the Applications folder. I suspect these can simply be trashed directly.
Other applications use a more complex installer, setting up folder and files in various places. A good example of this is SpringTools Suite, which puts the main application folder in the user's home directory and a working directory in the user's Documents directory. While some installers come with an "uninstall" option, some - such as STS - do not.
How can you safely and cleanly uninstall an application whose installer doesn't come with the option?