To suppliment Andy's advice - have a look through whatno's website.
Spectators have good views and photo ops, as i've seen Stuart and Sally Anne of WNN stood in the spectator areas to get their shots, along with they're shots from the marshal's posts.
some of the good places - Right down at the bottom of the hill at Chippies - depending on your lens you have them turning into and through the Esses before heading round Chippies and into Country,
Further up theres good photo ops round Farmhouse Bend.
Also right up at the top, the final Corner - Quarry, from the inside from the spectator side alot of good shots can be had as its a difficult corner for the drivers.
Theres also a footpath from the Hilltop carpark down to the outside of Clarks, but i dont think this has good photo ops as theres a Big Tyre wall and Receptico along there.
Finally, leave the paddock, cross the cattle grid, and turn left through the field. and follow the track to the end of the field, theres a gate here and a path down behind Quarry... i'd recommend a zoom/telephoto lens here as your a fair distance from the track here,
but carry on down this track and it'll lead you to a viewing area behind the Marshal's post on Orchard
All the pics here where taken by my wife while i was on post, so where taken from the spectator points.
Hope you enjoy the day there.