Adding an extra WFE in your existing SP Farm

Here's how that can be done:

1. Install Windows Server 2003 R2
2. Install IIS 6.0 
3. Install .Net 2.0,.Net 3.0,.Net 3.5
4. Fully patch the server with the respective service packs and security updates
5. In Internet Information Services Manager remeber to allow ASP.Net in the Web Service Extensions section. 
6. Join the server to the domain where the rest of the farm belong to, if you haven't already done so
7. Add the MOSS installation account to the local administrators group.

Note:- 

1. On WFE, you dont need to install SQL SERVER.
2. One of the most important thing while making your s/m ready to run in production,S/Ws should be installed properly.
3. Run your SP configuration wizard aftering making all upgradation i.e installing of all needed patches/service pack for moss
4. Install min SP2 for Sql server 2005 in your Application server to properly compete with MOSS 2007

Install MOSS and join the server to the existing farm

1. Install using the MOSS installation account
2. Start MOSS Setup, enter your license key and accept the license agreement
3. Select Advanced and Complete install
4. Run the SharePoint Product and Technologies Configuration Wizard
5. Connect to an existing farm
6. Enter the MOSS database server end click Retrieve Database Names. The Database Name and Username fields are automatically populated. Enter the password and click Next
7. In Advanced Setting make sure that this server will not host the Central Administration site and click Next
8.  That's it. The new server is now member of the farm. (Web Front-end, indexing etc)
9. Now  you can configure your needed services from "Services on Server" in Central Admin.