By far the easiest way to get started with Apache is to use the Apache server included with your operating system (if possible). As you become more experienced with Apache and you need to customize or extend it in particular ways, it is useful to build your own version from source. Hour 18 deals with extending Apache and describes several utilities that can help you do so.
The OpenPKG project provides a consistent way to install server software, including Apache, across a variety of platforms. It is a nice alternative to building Apache from source or using the Apache versions provided by your vendor. The OpenPKG project is open source, supports different operating systems such as Solaris, Linux, and FreeBSD, and it was started by Ralf S. Engelschall, author of several popular Apache modules. You can learn more about OpenPKG at http://www.openpkg.org.
The document at this URL describes how to get started compiling and installing Apache on Unix:
In the following URLs, you will find the equivalent information for Windows-based platforms, including compilation from source:
For advanced Apache users, or if you want to become involved in development, the Apache developers' site includes information on CVS access, applying patches, and so on: