Also, when you've tightened the top cap, before you tighten the stem bolts, put on the front brake, and roll the bike forward, until the rear wheel lifts off the ground.
If there's a clunk, the headset is too loose. Conversely if the steering binds, its too tight.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.