For those of you with other carriers, I had the same problem with my T-Mobile LG G3. Absolutely no information whatsoever, the G3 would never register on my PC. Of course, the government has forced them to put an invasive program on your phone now that gives them access to your PC in addition to your cell phone.
Once you plug your USB cable into your LG G3, you have to pull the notification menu down at the top from your main screen (where you would see all your notifications for Tweets, Weather warnings, etc.). It will show you a USB option and asks you to download the LG G3 Suite (again, now everyone has access to every piece of electronics in your home, work, etc.) to allow your computer access to your phone. When you press on the ok to install the Suite, it will do a bunch of invasive things to your computer, you'll have to save the program on your computer, install it, wait 5 minutes while it goes through your computer and hacks all your personal information, then FINALLY it will detect your phone and you'll see it in your file manager on your PC.
I'm not thrilled about it and if I didn't keep videos on my phone to watch while I have to wait for things I would never have installed the program on my PC to begin with. *growl*