My $.02?
4WD & as low a Tire Pressure as the rim will allow. I'd guess 15psi would be max. Any lower and you will have to be concerned with the tire slipping on the rim. The key here is to have as big a footprint as possible to prevent you from sinking in and even then it's always a possibility to have to contend with.
Keep your momentum going especially on any kind of upwards incline in sand. The moment you start to slow down or stop, your tires will start to dig into the sand. You want to avoid this. Of course driving this way, you need to know what's ahead of you on the other side of a dune so take care when doing this.
A shovel. Even one of the small folding military ones is fine.
Optional Items...
A winch with a good anchor (another vehicle, pull pal, buried spare tire, etc.) is nice to have if you really get stuck.
Sand ladders are another nice option to have especially if you do this frequently enough. You can buy them for as low as $150 for a pair of Smittybilts or pay more for other brands.
HTH.​