Tips to Use Razor (Dota2)

• Mekansm and Drum of Endurance are very strong alternatives to Vanguard due to its poor viability on ranged characters. Mekansm is the stronger choice, but if someone else on the team is going to get it quickly (meaning at roughly the same time Razor could farm it, not 10 minutes later) Drums help Razor keep on his target and also tanks him up.

• Consider Phase Boots instead of Power Treads, as they allow you to keep in tether range of Unstable Current.

• Yasha is a strong item to get after the core as it works well with Unstable Current and further increases the movement speed of Razor plus it grants you the opportunity to upgrade it into either the Manta Style or the Sange and Yasha based on different situations.

• Plasma Field can be manipulated by moving Razor around, since it centers around him. This can help you position yourself so that Plasma Field can hit right at its maximum range.

• Razor has very few escape mechanisms, but can be deceptively durable with Unstable Current if focused.

• Use Static Link defensively in larger team fights to ensure you can gain the maximum drain amount without putting yourself in a bad position.

• Eye of the Storm damages the lowest health enemy close to him, making this ability very weak near creep waves. Try to save the ultimate for isolated team fights, or use Plasma Field to clear the creep wave quickly to focus the damage on heroes.

• In team fights, it is Razor's job to Static Link for the enemy carry and steal their farmed up power for himself. Once a link has been established and the fight has begun, Razor may choose whether to use the stolen damage to smite the enemy supports, or kill the carry himself.

• Static Link will not be purged if Razor's target becomes magic immune during the drain.

• Shadow Blade is an excellent item on Razor because the invisibility will conceal the particles for Static Link and Eye of the Storm, concealing Razor's position.

• Refresher Orb allows two instances of Eye of the Storm to be active at the same time, allowing for extreme DPS and armor reduction, though it is an expensive and niche item.
  • Combined with Aghanim's Scepter, this can deal twice the damage to buildings.

• Generally in the early game, its best to pick up Static Link as it can boost your survivability by lowering enemy damage as well as allow you to create a noticable difference in you and your opponents last hitting power. This allows you to dominate the last hitting stage of the lane and keep your enemies in check

• Static Link is not broken by spells that pause the target such as Outworld Devourer's Astral Imprisonment or Shadow Demon's Disruption.. 

source: http://dota2.gamepedia.com/Razor