It often happens that while modelling you forget about the final details of your model and you need to go back and add a hole to your mesh. There are many different approaches that can be used but which one is the best? This video tutorial featured on BlenderNewbies is one approach that works really well.
Here's a quick video showing how to cut a hole in your mesh. This technique is useful for creating very clean holes, without the mess that can sometimes result from using booleans.
Be sure to check out the other Beginner level tutorials and discussions at BlenderNewbies. You can read more about the Video Tutorial here and you can download the movie below (remember to right click Save As):