Multiple vertex transform and other things

[salt サルト]

This is my method of making weapon in dota:
Sculpt > Cut high poly into half > decimate the half > and mirror
( Please tell me if there is flaw on my method )
.......
Back to the topic, I reached the stage "Decimate the half" , this is the result
http://oi59.tinypic.com/1zdsp42.jpg
Well...... some of the vertices is displaced, so I want to make all of the displaced vertices into X : 0.0
Usually, I select each vertex and type 0 in the Transform X axis at a time ( It wasted my time a lot ), If I select multiple vertices and type 0, it will only move it into the median point
So, how do I make all of this vertex into X : 0.0 instantly?
........
unrelated to the topic :
Am I supposed to unwrap the lowpoly before sending it to xNormal ?

[Akaize]

Well, My method is totally the opposite, I model the Lod 0 with care, map this with care, and after this, I create a copy and increase the edges count in hard corners, and use the modifier "Multi-Resolution". With this, I use the sculpt, and map the normal map.

well, I don't know what method is the best. But I think reading this one, will give u some ideas.

Thi is a sword that I make with this method.
http://i.imgur.com/kG88CWP.png?1

[salt サルト]

*fix
My method actually :
Make medium-poly ( lod1 ) , sculpt and so on.
. nice methods there...
What option do you use to bake normal map in blender ?

[Akaize]

Well, I select the High poly, and the lod0 (in this order), and use the Bake.
Normals - Tangent. Margin 32, Split-Fixed.

LOD 0 is the portraid model, LOD 1 the game model.