It’s very handy to have a PowerShell script automatically load when PowerShell starts up to configure your environment, like an AutoExec.bat in the old DOS days.  Here’s how I have mine set up.

1. Tools Dir & Env Var
   I keep a general Tools directory on my machine with command line tools, scripts, etc and so set a system environment variable called tools that points to this directory.
2. Run Unsigned Scripts
   Run set-executionpolicy bypass once in each environment (cmd shell and ISE) to allow easy execution of unsigned scripts.
3. Profiles Auto-Load Script
   PowerShell supports profiles with an auto-load script on PowerShell start up.  Simply put the files Microsoft.PowerShell_profile.ps1 (for basic shell) and Microsoft.PowerShellISE_profile.ps1 (for the GUI) in your %UserProfile%\Documents\WindowsPowerShell directory. These will be run on PowerShell startup.
4. Consolidate Scripts
   The only line I have in these files is: ."${env:tools}\PSScripts\PowerShellEnvironment.ps1" to launch my ‘real’ script. This make it easier to manage, with only one file that’s near my other powershell scripts instead of the two separate scripts above.
5. Chain ‘autoload’ Scripts
   Then it helps to separate into individual scripts various aspects of your environment setup.  Like a script for aliases, itunes, functions, regular expressions, favorite assemblies, etc.  So I have an ‘autoload’ directory with these scripts in them to chain load. Here are the contents of PowerShellEnvironment.ps1:

# directory where my scripts are stored 
$psdir="${env:tools}\PSScripts"

# load all 'autoload' scripts
get-childitem "${psdir}\autoload\*.ps1" | %{.$_}

Write-Host "Custom PowerShell Environment Loaded"  

6. My ‘autoload’ Scripts
   Here is a snapshot of my autoload directory of scripts in case you’d be interested.  PowerShellScripts-autoload.7z

That’s all there is to it.  One of the reasons for putting this out there is so that I can now reference it from other posts too.  :)