What is right?
1) "well know" or "well-know"
2) "non central" or "non-central"
There some general rule?
The rule is that you hyphenate double-adjectives only if they come before the noun they modify. For examples:
Brad Pitt is a well-known actor.
Brad Pitt is well known.
"Non-" works differently because it is a prefix, not a stand-alone word (as opposed to being stand alone [see the hyphen-usage difference (as opposed to the difference in hyphen usage)]).
Hyphenation of compounds is something that different style-guides differ on immensely; different people use different variants of the rules while all being correct.
Both of your cases here are adjectival compounds (assuming you meant "known" rather than "know"), but they differ in how they form them.
"Well known" or "well-known" is a combination of an adverb and an adjective. Different policies people might apply here are:
Hyphenate unless the adverb ends with -ly: Hence "well-known".
Don't hyphenate unless the adverb has an adjective sense (true of well) and could potentially be intended as applied to the noun: Hence depends on what we are saying is well-known.
Don't hyphenate unless the adverb has an adjective sense, but then always hyphenate: Hence well-known.
Generally also, hyphenation will only happen if you are using it before the noun, so someone who would write "a well-known writer" would say "the writer is well known". But if a phrase has its own hyphenated entry in a dictionary someone is using they might hyphenate even after the noun.
In the case of non-central you have a prefix non- that does not operate on its own. Here the choice is not between hyphenating and leaving it unhyphenated, but between hyphenating and closing; "non-central" vs. "noncentral".
There is even more variance found here than in the previous case. The simplest rule to follow is just to see if the compound has its own entry in the dictionary you are using, and to use it as the dictionary does if it does, and hyphenate otherwise. Another rule some people follow is to close it (noncentral) unless the result is confusing or results in producing what is already a word with a different sense.