To answer your particular question, for a 4GB production server, you are limited to using the /3GB switch. The /PAE switch is only applicable to OSs having more than 4GB of RAM. For this reason, you will most likely be using a Standard Edition of SQL Server, which does not support AWE.

A number of things to keep in mind:

Firstly, the article starts by discussing the two switches, which is related to the OS. Use the hyperlinks to check that your particular operating system support the two switches.

Secondly, determine if your particular version of SQL Server supports AWE. Again use the hyperlinks to check.

Thirdly, determine if you wish to configure (i) BOTH switches with AWE enabled for SQL Server for systems with between 4 and 16 GB of RAM, (ii) just the /3GB switch for systems with less than 4GB RAM or (iii) just the /PAE switch with AWE enabled on SQL Server for systems with more than 4GB RAM.

Lastly, set the max memory setting for SQL Server to a value that is right for your system. This is the 'tuning' part, where you may need to change the default value when AWE is enabled on SQL Server. The default value may be appropriate for a 'dedicated' Database server. My production servers are on SS2K EE with 7-8 GB RAM, and I have the max memory setting set to around 1 GB. Whatever value you set, you may need to monitor it for a few days. HTH.