As I start developing in node from scratch I want to do it right. First thing I want to do is set up Intellij to work with node.
Install NodeJS Plugin
This assumes you have NodeJS installed on your system. To check if it is installed you can run the following from command line.
> node -v
I am using this page as my install guide https://www.jetbrains.com/idea/help/node-js.html 
Open up Intellij I am running version 14.1 Ultimate Edition.
From the File menu click on Settings.
Select Plugins, then click on Browse Repositories
Search for nodejs, and install the NodeJS plugin
The download runs
Click Restat Intellij IDEA
For some reason it does not restart, but that window does close. Click Apply
Configure the NodeJS plugin
From the File menu click on Settings
Under Languages & Frameworks Click on "Node.js and NPM"
Confirm that the Node Interpreter is correct and the correct version, if it's not set it up.
Configure the Core Modules
If I am reading this right you need to Configure the Core Modules for NodeJS if you want
· code completion
· reference resolution
For NodeJS core modules (fs\, path, http, etc.)
So how do you set this up?
This is my second time installing nodejs and it looks like it remembers my configured module (In fact I tried to make it forget to no avail)
I installed Intellij on another machine to show you how to configure it.
Chances are you have this, Source are not Configured.
I am going to let it download the modules.
The download starts.
Click Edit Usage Scope
I am not sure on this screen… I think it's OK, click OK.
Create a new Node/Express Project
From the File Menu select New -> New Project.
Select Node.js and NPM and click Next.
Give it a name and click Finish.
Oh! This popped up when the project was created. Maybe it needs to be configured per project.
OK, looks like I have a basic set up.
Run the program.
Looks like it started and is running on port 3000.
Nice it's working
I opened app.js and tested out the code completion. I added this to the top and low and behold node code completion.
npm, adding module
What is a simple way to add a module to a node project in Intellij?
First let me try the terminal. (I am going to install the bootstrap module)
Did that work?
Looks like that worked just fine J
After writing this I kept having issues when I created new Node Projects, I had lost my auto completion.
To really fix it I found this post showing how to fix this. http://www.fse.guru/nodejs-autocomplete-in-idea-and-webstorm 
To fix it do the following.
From the file menu select Settings.
From the pull down select "TypeScript Community stubs".
Scroll down to node and click Download and Install.
After it downloads make sure it is enabled globally, click OK.
Now you get code Completion.
 Intellij Help node.js
 NodeJS Auto Complete in IDEA