By now, most Android phones have a 4G antenna -- but lots of 4G networks are spotty, and sucking down data at that speed can drain your battery or put you over your monthly data allowance pretty quickly. What's to be done? The easiest fix is to manually select between 3G and 4G networks -- for example, maybe you only want to turn on 4G when you're in an area that has good coverage, or maybe you want to force your phone onto 3G to avoid draining your battery. Look for the "Mobile networks" subsection of the Settings screen, then check "Network Mode." You can set it to CDMA only (3G), or LTE/CDMA (3G and 4G). This setting might vary depending on where you're living or what network you're on.