A further thought: if wanting to transfer files by USB, it's a good idea to check that the cable you're using is the right kind for data transfer. Some cables that come with phones are meant only for charging purposes, and you can't tell by looking at 'em.
ADDED LATER:
I just downloaded "Android File Transfer" and tried it out, connecting my Mac Pro to my Samsung tablet. It worked! In fact, it worked rather TOO well for my liking. As soon as I connected my tablet to the Mac, AFT launched its finder-like window and showed me the contents of my device. "Great" I thought ... and then it hit me that the tablet had not required any authentication/login procedure to do this. Gulp.
...so ANYBODY armed with a copy of AFT and my (stolen? borrowed?) phone or tablet would be able to access all of its contents.
My phone and tablet are both pretty old, running Jellybean. I can only hope that more up-to-date versions of the Android OS have plugged this gaping security hole!