Vendetta recently posted how to rip a DVD with windows. I will explain how to do so with OSX.
First, you will need DVD ripping software. I use MacTheRipper which can be downloaded for free here. (MacTheRipper).
1. Open MacTheRipper and put the DVD you want to rip into your disc drive.
2. Wait for the DVD to load up (a red bar will go across the middle of the program).
3. The default location for the DVD to save is on the Desktop. If you want it to save elsewhere, Go to File >> Save To... and select a different save location.
4. If you click on the Mode tab, you can choose whether you want to extract the whole DVD or certain parts of it. If you just want the actual movie, choose "Main Feature Extraction".
5. Click Go.
5. The DVD, depending on the size, can take from 5 minutes to an hour to extract.
6. Once the DVD is done extracting, it will be stored in the directory you specified. The files will be in a folder named whatever the DVD was called.
7. Congratulations, you just ripped a DVD!