To enable PowerShell remoting (from one computer to another that are in the same domain), following steps 1 and 2:

1: Install PowerShell and WinRM

This comes as standard on Windows Server 2008 and Windows 7. If you need to install this on Windows Server 2003 for example, then downloaded and install the free Windows Management Framework Core Package (http://support.microsoft.com/kb/968930) from Microsoft.

2: Enable-PSRemoting

Run PowerShell as an Administrator (Start > Programs > Accessories > Windows PowerShell and right-click on Windows Powershell), then type in:

ps> Enable-PSRemoting

As follows (I have already run it so get a slightly different message than what you will get if you haven't already run it):

Windows PowerShell
Copyright (C) 2009 Microsoft Corporation. All rights reserved.

PS C:\Users\Administrator.DOMAIN> Enable-PSRemoting

WinRM Quick Configuration
Running command "Set-WSManQuickConfig" to enable this machine for remote management through WinRM service.
 This includes:
    1. Starting or restarting (if already started) the WinRM service
    2. Setting the WinRM service type to auto start
    3. Creating a listener to accept requests on any IP address
    4. Enabling firewall exception for WS-Management traffic (for http only).

Do you want to continue?
[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend  [?] Help (default is "Y"): Y
WinRM already is set up to receive requests on this machine.
WinRM has been updated for remote management.
Created a WinRM listener on HTTP://* to accept WS-Man requests to any IP on this machine.
WinRM firewall exception enabled.

Confirm
Are you sure you want to perform this action?
Performing operation "Registering session configuration" on Target "Session configuration "Microsoft.PowerShell32" is
not found. Running command "Register-PSSessionConfiguration Microsoft.PowerShell32 -processorarchitecture x86 -force"
to create "Microsoft.PowerShell32" session configuration. This will restart WinRM service.".
[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend  [?] Help (default is "Y"): Y
PS C:\Users\Administrator.DOMAIN>

On the controller, I can now run:

PS C:\Users\Administrator.DOMAIN> Enter-PSSession TARGET_MACHINE
[TARGET_MACHINE]: PS C:\Users\Administrator.DOMAIN\Documents>

And you can exit the session, by doing:

ps> Exit-PSSession

NB If you try and do it using IP address, then you will see:

Enter-PSSession: Connecting to remote server failed with the following error message : The WinRM client cannot proces
s the request. Default authentication may be used with an IP address under the following conditions: the transport is HTTPS or the destination is in the TrustedHosts list, and explicit credentials are provided. Use winrm.cmd to configure TrustedHosts. Note that computers in the TrustedHosts list might not be authenticated. For more information on how to set TrustedHosts run the following command: winrm help config. For more information, see the about_Remote_Troubleshooting Help topic.
At line:1 char:16
+ Enter-PSSession <<<< 192.168.88.133
    + CategoryInfo : InvalidArgument: (192.168.88.133:String) [Enter-PSSession], PSRemotingTransportException
    + FullyQualifiedErrorId : CreateRemoteRunspaceFailed

(even if you add it to the trusted hosts it seems)

3: Enable Trusted Host (if not in domain)

I haven't tested this, but if you need to allow PowerShell remoting to a non-Domain member, then you will also need to add the remote computer to the local computer trusted hosts:

ps> set-item wsman:\localhost\Client\TrustedHosts -value <RemoteComputerName>

NB Only members of the Administrators group on the computer have permission to change the list of trusted hosts on the computer. If you need to add a number of computers to this list, you first need to use get-item, set it to a parameter, then add to that - see reference link. You can confirm the computer is listed by doing:

ps> get-item wsman:\localhost\Client\TrustedHosts

Also note:

# You need to set a password on the remote computer.
# You need to use the Credential parameter in all remote commands.
# Confirm that the ports are open between the machines (80/443 depending on what you have enabled) on the machines and any firewalls.

To see if unencrypted traffic is enabled, run:

ps> cd WSMan:\localhost\Client
ps> dir
Name                      Value
----                      -----
NetworkDelayms            5000
URLPrefix                 wsman
AllowUnencrypted          false
Auth
DefaultPorts
TrustedHosts

To set "AllowUnencrypted" (i.e. you want to run on port 80), run:

ps> set-item -force WSMan:\localhost\Service\AllowUnencrypted $true

This probably needs to be done on both the remote computer and the controlling machine. You may also need to set the DefaultPorts:

ps> set-item -force WSMan:\localhost\Service\DefaultPorts -value <port>

You may also want to enable Digest Authorization:

ps> set-item -force WSMan:\localhost\Service\Auth\Digest $true

References:

about_Remote_FAQ
http://technet.microsoft.com/en-us/library/dd315359.aspx