Hello, this is my first build on mobafire, so please go easy on me. :)
My main is actually Noc, but I recently purchased Vayne. She is very squishy but can be a royal pain in the ***. Whether you are playing against a tank or squishies, you are pretty much guaranteed kills. Many people despise Vayne for how OP she is but in reality it isn't that difficult to kill one imo. Anyways here it goes.

My rune setup is rather simple even AFTER they nerfed Vayne. I have 9 ArP marks, 9 flat AS seals, 9 flat AS glyphs, and 3 ArP quints. I have considered adding CDR runes however, the extension of her CD doesn't seem to be too bad. However, these could be beneficial in place of the AS glyphs.

23/6/1. First off, I put 23 points in the offensive mastery tree. The crits seem to work nicely with Vayne's attacks. Especially during early game Vayne doesn't do as MUCH damage so I figure it works out nicely. The CDR and bonus attack speed seems to be a must seeing as her skills are spammable and she is an AWESOME DPS. The magic spell pen and armor pen helps her take out tanks with little to no effort as well. Also, who doesn't like increased damage? :P

I went with 6 points in the defensive mastery tree with 3 points in armor and 3 points in MR. The reason for this is, Vayne is really squishy so any bit of help with her survivability is nice. :)

Last, I put 1 point in Haste. This is another plus for a squishy. It helps in instances when you need to run your *** off.

I start off with Doran's Blade. I really do not like starting with a Doran's item when I play but it does have a lot to offer for someone like Vayne.

I then, grab berserker greaves for the increased MS and AS. At level 3~4, this could be very beneficial. (I prefer grabbing Boots of Speed and pots before grabbing the dagger if I cannot complete the build at once.)

The next item I begin to build is Trinity Force. It's a great item for Vayne in that it gives a little of everything. The increased movement is a great plus to Vayne's passive, the effect of Sheen is nice for Vayne's Silver Bolt ability (though the AP it gives really isn't necessary) and the mana is always nice, Phage's Health and damage are really nice as well. I start by building sheen first, Zeal, and then Phage (if not complete Tri. Force).

After this is done, I build Madred's Bloodrazor. Now, Trinity Force and Madred's is a MUST for Vayne imo. Madred's offers good AD, good AS, and the passive tears tanks and any champ with alot of health a new one. When building this I grab Recurve Bow first, then Pickaxe, and finally Madred's Razor or complete the build.

It's now time to work on LS. Bloodthirster or Stark's is preferrable. I usually get enough kills by this point to be able to afford a Bloodthirster. I also prefer grabbing this instead of Stark's in that it gives you damage. Of course I grab the Vampiric Scepter first because it's just a pain in the *** going back to base after every gank/ team fight.

If the game is successful enough or lasts long enough (most don't), you should now grab an Infinity Edge. At this point I grab whatever I could afford first. :P

After getting my Infinity Edge, I sell my Doran's and grab a Black Cleaver. Again I go with what I could afford first while building this.

I start off with tumble. Flat and simple. It IS Vayne's main skill and does the most damage. I also max this skill first. At level 2, I put a point in Silver Bolts, and max this skill second. At level 4, I put a point in Condemn, and max this skill last. Considering the way I play Vayne I only use it for the stun. Finally, and obviously I grab my ult at level 6 and put a point in this whenever possible.

Ghost/Flash: I go with ghost and flash for survivability.

I have also seen ignite/flash, exhaust/flash or ghost, ignite/ghost. I really don't think ignite is necessary seeing as you will usually kill the opponent just by condemning and tumbling. Exhaust doesn't really seem necessary due to your passive.

But whatever works for you. :)

Pros:
-Fun to play.
-Will most likely get lots of kills.
-People will hate going against you.
-Easy multiple kills.
-Spammable skills.

Cons:
-People will ***** about ks'ing.
-Squishy.
-Ugly.
-People will yell at you because you keep killing them.

Team work is crucial for Vayne. You must have a well balanced team and laning with a tank would be awesome. While engaging in team fights position yourself behind or near a tank or support.

I wanted to add a section for "tumble dancing". :)
As, the name implies I like to tumble around and hit the enemy from all angles. :D
This helps with dodging and will annoy the opponent like no other! Enjoy!