Dark Blue and Black spots on a Base Model

I apologize in advance in being abrupt with this, as this is my first post with this forum(Hello to all of those people here by the way)and I don’t know if this is the best place for this post.

Anyways, I am having a basic problem with my mesh, in that in certain spots while making my mesh the mesh surface itself changes into either a dark bluish or black color, and its only in certain areas where this has been happening. I’ve been working with blender for a few months, and it has been a slow and enjoyable process, but I am wondering what I have been doing wrong in this case, and if any of you could help me out with this problem that I have been experiencing. Thank you in advance for the help, as I really appreciate it.

No screenshots or blend files to look at !!

Check your materials, have you assigned the wrong material to the wrong faces ?
Check for duplicate meshes overlapping. If so delete the duplicate
Check for duplicate vertices (select all mesh and W / remove doubles). Then physically check

Basically don’t be scared of actually looking at the areas that don’t look right. select a vertex and move it, does it look correct or not

for future help please ALWAYS supply a link to your blend file and show us what is wrong. Telepathy should not be a prerequisite of using the forum

I apologize for not posting my file I wasn’t thinking when I posted it last night. Anyways, here is the .blend file
Alien Soldier.blend (649 KB)

And I guess you could say that this is a sort of example as to most of the recent problems that I have been encountering in Blender, and that this is the most recent form of what I’ve been working with. I’m sorry for causing anything that might have been frustrating.

Thanks for the assistance, It makes the model look much better(I think.)