The only skippable book is book 10, Crossroads of Twilight. Book 6, Lord of Chaos, is actually awesome. The rest have a lot of slow segments but when they're good, they're just as great as the earlier books.
But once you get to book 7, you should have a good enough feeling for the series to be able to tell when someone is about to happen. If you get to a chapter involving all females, skim the chapter and read the summary that Terrd posted. Anything involving Rand or the Forsaken, for example, is always worth reading. You'll get the hang of it.
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