Park in Amesbury and walk up Stonehenge Road, cross the A303 at New King Barrow (where there's an island in the middle) and walk alongside the north side of the A303/A344 in the field (NT open access land). It's 2 miles though. Or, park somewhere in Larkhill (this isn't as easy as there are no car parks, but most of the roads are quiet and double yellow free) and walk south down byway 12 (starts at the south west corner of Larkhill, where Fargo road turns into Willoughby Road). That's about 1 mile. Last year byway 12 was completely chocka along its entire length, on both sides of the A303 and all the way north well past the Cursus and into the trees. It actually filled up the night before quite a lot so I won't be relying on it (well, I don't actually need to anyway!). This is all weather dependant though, but if it's nice it can be a very pleasent walk. you get to see a lot of the other monuments on your way, and get a good appreciation of King Barrow as you walk up Stonehenge Road.