There are two routes out on foot - one is shorter than the other and involves crossing a creek containing deep mud and quick sand. The second is longer and slightly safer, but also involves crossing a muddy creek as well as a small estuary. I think most people would advise against trying to make your own way out there unless somebody is willing to show you the way out there - that was how I learnt the routes. Both are dependant upon crossing the creeks at the low point of the tide.
A safer third option would be the charter operating out of WNTS harbour, which will take you out and drop you off for a fee - a service which in my opinion has totally ruined the place, with hooray Henry's crawling all over the dunes having a spot of luncheon.
Hope this helps!