I'm trying to figure out what style guidelines or rules apply to creating compound adjectives when adverbs are involved. Typically you create compound adjectives when there is potential for ambiguity between the noun and the previous modifiers(s):
This is a high-risk behavior.
But you don't typically hypenate 'ly' adverb pairs (I believe).
This is a highly risky behavior.
While the example above looks correct to me, the example below just feels somehow wrong.
That is a friendly looking dog.
It should be be:
That is a friendly-looking dog.
Is there a general rule or style guidance for when a compound word is preferred over leaving the modifiers separate?