I don't pretend to know what makes a good or bad helmet, I am very new to the motorbike scene and have a lot to learn. But my wife bought her new motorcycle helmet recently and it quite possibly has the best safety feature I have ever seen and I now believe every helmet should come with these as standard. Plus it is extremely cool to boot!
Built in LED lights both front and rear!
Here is a good in-depth review of the Shark Skwal helmet.
And here is their brochure video.
Be safe out there budding motorcyclists.
On a side note it appears that my wife and my 5 year old have almost the same size head.