You can go Unyielding Pressure against Yago, as you gain extra percentage based damage on your dark siphon (650 when in her travel form, 390 when planted).
This is a tip for Lex VS. any champion.
When chasing down your target, don't blindly follow them.
It's best to let them walk into your hands, cut them off around corners.
Line up your crosshair with their head, for an easy headshot.