When fingering a chord, most people put their fingers down in numerical order. Sometimes that's right; many times it's wrong.
When strumming with a pick, place the fingers down in the order in which the pick strikes the corresponding string. That way you can actually start the strum before you get all your fingers down, gaining a split-second of time.
When finger-picking, place whichever fret-hand finger is on the string that is plucked first. You don't need to have all fingers down before you start picking. This will save a split-second of time.
And saving a split-second of time can save your ass.
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