Last time I was there, the grandstands were open to all-comers during the two practice sessions. Good chance to peer down into the pits from directly above and suss out which grandstands to book on a return visit.
The main problem is getting a view around the heavy safety fencing.
There's not many good spots, but the best I found were on the infield just before Tetre Rouge, the right hand end of the banking at Porsche Curves, from the top tiers of the Maison Blanche grandstand (T23) - and the big wheel.
There's also a good night shot from Maison Blanche as the cars brake heavily into the Ford Chicane - 1/20s panning doesn't show the wire and patience will be rewarded with red hot brake discs and flames from the exhaust.
The loony antics of the campers are always worth photographing.
Last two times I was there we positioned ourselves for storming the trophy presentation on the start finish straight, one time getting close enough to get soaked by the champers. Well worth the effort both photographically and just to be there!
It's usually roasting hot and the distances between viewing points are vast.
Minimal kit, lots of water, hat and light coloured clothing are the only sensible option!
During the race I've only seen one instance of theft from the tents, less than 10ft from where a large group of us were sitting; there's no major problem, just be sensible and don't leave valuables in the tent. However - as already mentioned; post-race security is not the organisers strong point (non existent); best to get back to the campsite as soon as the race finishes or your BBQ, chairs and everything else may have walked.