Their usage is pretty complicated. I would read http://www.englishpage.com/minitutorials/sosuch.html Such can be used with certain types of nouns and with adjective + certain types of nouns. So can used with adjectives and adverbs and words like "many", "few" + noun and words like "much" and "little" by themselves.

We use “so” when we are describing an adjective (good, bad, hard, easy, mean, nice). For example, we say “The acting in the movie is so good.” We can also say “The test was so hard”. We can say "She is so mean". "The teacher is so nice". "The dolls are so pretty". "The children are so good". But when we describe a noun (people or things), we have to use “such”. For example, we can say “He is such a good actor”. We can also say “That was such a hard exam”. "She is such a mean teacher". We can also use "such" with plural nouns. For example, we can say "They are such good children". "They are such obedient dogs".

When we use the word “so”, it is followed ONLY by an adjective. When we use the word “such”, it is followed the article “a” or “an”, then by an adjective and finally, by a noun. Sometimes there is no adjective in the sentence at all. For example: My friend is so nice. My friend is such a nice guy. My friend is such a gentleman. It’s so hot today. It’s such a hot day today. It’s such a scorcher today. Harriet is so intelligent. Harriet is such an intelligent woman. Harriet is such a genius.

SO with adjectives and adverbs so + adjective/adverb + that + result The sun was so strong that they got burned within 15 minutes. SUCH + Nouns such + a + (adjective) + singular noun + that + result (It is common to put an adjective before the noun) Christopher is such a handsome man that all the ladies want him. such + plural/uncountable noun + that + result She has such big feet that she has to buy special shoes. http://www.grammar.cl/Notes/So-Such.htm