Frost is unique among casters. Every other caster in the game calculates if their spell is going to Critically Strike the moment it leaves your hands. Due to Winter's Chill wanting you to cast an Ice Lance directly afterwards, but being unable to be applied to the target at long distance before the Global Cooldown is up, Blizzard changed when Frost's spells check their Critical roll to the moment of impact. This moment of spell checking allows for the slower traveling Glacial Spike, Ebonbolt, and Frostbolt to be launched first, but impact after the first bolt of the extremely fast Flurry, assuming it is cast directly afterwards. It is this cast time spell → Flurry → Ice Lance combo that is the heart of Frost, and it is this combo you must master to be competent in the spec, regardless of talents chosen. In addition, Ice Lance also has a fairly fast travel speed, and should always follow up any Flurry cast with Brain Freeze. Winter's Chill will consider the target frozen—Ice Lance will Shatter and gain the triple damage benefit, just as if it were cast under Fingers of Frost. And again, since Frost's spells calculate their Critical status on the moment of impact, you should cast it immediately afterwards rather than wait for Winter's Chill to apply to the target. The travel time involved will make sure your Ice Lance always benefits from frozen status. Waiting will make you miss the window.