There are hundreds of articles and many SE QA's about moving apps to an external SD card.
Some of the articles and QA's are outdated, some are incorrect, some require the device to be rooted, some require additional partitions to be created, and some require specific apps that cost money or include ads.
I stumbled on this article, which described a technique that seems unbelievably simple: http://www.howtogeek.com/114667/how-to-install-android-apps-to-the-sd-card-by-default-move-almost-any-app-to-the-sd-card/
The crux of the article can be summarized in a concise manner. It states that the key is running this simple adb command:
adb shell pm setInstallLocation 2
This technique is free (gratis), ad free, and requires no extra software or partitions on the Android device.
But does it work? Is it reliable?