Focus allows for many interesting tactics at level 1. Having a crit at level 1 and Volley allows you to burst someone instantly for around 250~ damage, this combined with a stun can be deadly. Ashe is one of the scariest champions to deal with at level 1, as she can invade or defend against invade easily.
Q: Frost Shot
Frost Shot allows Ashe to kite, since it's on her Auto and Volley, it makes catching an Ashe essentially impossible if you don't have Flash. 35% Slow on auto's just scale incredibly well into late-game.
Volley is insanely strong level 1 - 3, then becomes sort of weak since the base damage increases on it is horrible. However the cooldown reduction you get when you level Volley is amazing, allowing for an almost permanent AoE slow combined with Frost Shots.
Hawkshot is maxed last, even though it gives extra gold while killing creeps. Hawkshot is a great scouting tool, incase a ward drops on Dragon/Baron, or if you think you're getting ganked. Hawkshot is also a great play-making tool allowing your jungler to gank easier or hitting a Crystal Arrow.
R: Enchanted Crystal Arrow
Enchanted Crystal Arrow is one of the best initiations in the game. It can completely swing the game around in your favor if you can land this ultimate on a critical target, or catch enemies offguard or in transition.