However you have travelled here you are here to see the amazing views and as walking around is a key part of the experience ensure you have comfortable walking shoes, (we love Hotter shoes, for total comfort and they look great too).
The temperature in the Canyon can be surprisingly cool even in the summer (June, July and August) so dressing in layers will help you manage the change in temperature. This is particularly relevant if you are on a day trip from say Las Vegas where you will be used to hot weather. There can be as much as a 22C degree difference between the two locations.
You'll still need sunscreen (we love the Riemann P20 range for 10 hour protection), a sunhat and sunglasses.
Casual, loose layers are the key to being comfortable.
If you plan to do any walking down in to the Canyon then you will need good walking boots.
Remember your camera and lots of film or memory.
The very best way to see the full majesty of the Canyon is without doubt in a helicopter,in our view it is an absolute must do.