There are a few possibilities; dictionaries usually go by (number of strokes in the radical) + (number of strokes remaining). Because there are too many chara

There are a few possibilities; dictionaries usually go by (number of strokes in the radical) + (number of strokes remaining). Because there are too many characters, there's usually a phonetic-based system involved too (Pinyin, Zhuyin, Kana, and Hangul); those have internal sorting, and that can be used too. This is all separate from, say, Unicode code point ordering.