Yes, there are standards, but they are flexible.
/usr indicates user-available files; /usr/local usually indicates user-available files that are user-installed. As you may already know, KDE, for example, uses /opt (meaning "optional") for its main file locations, so that is also a possibility.
I would suggest doing what you find most comfortable and easy to remember. You could also do a "locate programname" to see where other programs of the type you're installing are located, and then install them to the same prefix (/usr, /usr/local; /opt; etc).
Hope this helps.