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Most manufacturers recommend charging your battery until full for the first time, but it's really just to teach your phone the capacity of the battery. You really should do it once. Let your battery drain all the way down until the phone shuts off. Then plug it in using the charger, not the USB cable in a PC. When it's full, unplug it and reboot, then shut it off and plug it back in. If plugging it back in turns it on, shut it off while still plugged in. Let it charge for at least another hour, even if it says full. Then you're good.
Modern LiIon batteries do not have a memory so you'll be okay with small charges. Actually, deeply discharging the battery over and over can harm it, so try not to let it get down to zero too often.
