A. use so + adjective/adverb (e.g. so quick, so quickly) and use such + noun (e.g. such a book, such people)

B. So and such make the meaning of an adjective (or adverb) stronger (e.g. We had such a good time)
B1. use so and such with the meaning “like this” (e.g. I didn’t realise it was such an old house.)
B2. so long vs. such a long time; so far vs. such a long way; so much, so many vs. such a lot (of)