Hi everyone First of all my english isnt so good so please dont flame me for it.
In the past I have alot of trouble with Vayne. Always first target so I cant do anything.
So I made a build for Vayne and I hope I can help some people with it.

First of all. Vayne is a very hard ranged carry to master. She does some great damage but also she wil also get killed very easy. So its really hard to master her. My playstyle is defensive. Some are flaming me for it but I dont care. Because Vayne is one of the best assassins in the game you will get targeted and champions like tryndamere will always get you down. So always stay back against strong melee's. Focus on mages , ranged carry' and tanks. Always start with the mages. When you are in a team fight always wait until everyone is in combat. After they are all busy then you strike. Pick the weakest champions in the most case its the mage/support or ranged carry. But because of Vayne's silver bolts she is very strong against tanks. After you get the weakest I recommend you go for the tank and get him away. Dont focus on any strong melee's and especially dont try them 1v1. Unless you can stun them with condemn. Other wise you would die in the most cases. I hope I will help alot of you who have troubles with Vayne. Good luck with her and enjoy it:)

For runes I like to pick alot of armor penatration. So I can hit tanks pretty hard. I also got magic resist and armor runes. I pick those so runes because I dont wanna die in 2 secs.

My summoner spells are ghost and exhaust. I got ghost for escaping and exhaust for getting the kill.

Pros:

Very strong against mages and tanks.
Strong early game can easy push lane.

Cons:

She needs to be on distance melee champs will kill her quite easy.
Always first target.