I have to agree with others about the astonishing atmosphere here – it is probably the most breathtaking site of its kind I have ever visited (in 2002, in my case), too.
Some practical notes: the main marks are to be found on the north side of the top of the hill: there’s a gate which a farmer has sagely put into the fence that divides his land from the actual Old Bewick Hillfort. The OS Explorer map is a bit misleading with its ‘Cup & ring’ label.