Keeping code safe is important for any project whether it's big or small, and it can sometimes be important to revert changes - this is where version control comes in. Subversion is one of the most popular version control systems available and this article shows you how to use it in *nix or Windows.
Installing Subversion in Linux
Assuming you have apt-get, you can use the following commands from the bash prompt:
apt-get update apt-get install subversion apt-get install libapache2-svn
This will install all the components required for setting up SVN and for using WebDAV with Subversion.
Installing Subversion on the Mac
On OS X you can install Subversion in a variety of ways from Tigris.org -which include using Fink, a program similar to apt-get on Linux. One of the methods is a nice and easy to use .dmg which is a universal binary that is available from CollabNet.
Installing Subversion in Windows
With Windows there are two easy ways of doing this. The first is to use TortoiseSVN which is an easy to use GUI that can create repositories, checkout from the repository, commit, and pretty much everything else you can do with SVN from the command line (or bash prompt!). This comes as both 32-bit and 64-bit versions though I've found the 64-bit version to be a little unstable under Windows Vista.
The other option is to not use a nice GUI, and to instead use the command-line like on other operating systems. To go down this path you will need to download and install SVN for Windows.
Now by this point, no matter which platform you're using you should be ready to create your first repository. We can talk about connecting remotely to repositories later.