I take Mana regen runes for the more frequent harrasment of nimbis strike and crushing blow.
I take Flat attack damage for the rest of my runes making sure to take the early and late game to my teams win.
For masteries i take mana per level and mana regen for the harrasment again like in my runes.
Also, i take 21 points in offense focusing on damage, crit, attack speed, and the small pecent of life steal.
For boots you can take the boots of speed first or go directly to getting the berserkers greaves. Also rushing trinity force will be a great start on this build, because you can harras much more offen in early game.
This ability sequence is the most common harrasment sequence because you will deal damage and the you can just walk away from your enemy while stealthed.
This sequence is for chasing targets mainly.
This will surely give you a kill if your target is low on health and he doesnt see you coming.
For summoner spells you can take Cleans instead of exhaust if the opponent team has a bunch of stunners, slowers, etc.