Upgrade from iPhone 4 to 5s (both 16G) 'other' file now exceeds capacity

When I traded in my iPhone 4 in for the 5s (both 16G), I went from having about 40% open space to not being able to fit in my 700 iTunes library on the 5s. Nothing was added but the 'other' indicator is now way bigger and filling up most of the capacity. Can anyone help with what I need to do to clean that out?