Hyphens

When does one know to use a hyphen for something? Seriously?

I kind of knew this rule (from grammarbook.com):

Rule 5When adverbs not ending in -ly are used as compound words in front of a noun, hyphenate. When the combination of words is used after the noun, do not hyphenate.Examples: The well-known actress accepted her award.Well is an adverb followed by another descriptive word. They combine to form one idea in front of the noun.

The actress who accepted her award was well known.Well known follows the noun it describes, so no hyphen is used.A long-anticipated decision was finally made.He got a much-needed haircut yesterday.His haircut was much needed.

But for the other rules--there are 16 total, 8 that refer only to hyphens with prefixes--I'm overwhelmed. One rule even says that to know for sure, you must look up a word in the dictionary. I don't have one of those in my head--but I guess it gives me more reason to use my favorite app on my phone. As I looked at all the rules, I realized that this is one area of grammar where it makes more sense just to look things up when there are questions. The rules are way more specific than it makes sense to memorize.