When you start to slow, steer left/right/left to help front tires grab new sand. Once you stop moving then stop. Any tire spin at that point will just dig down. Sand is where you want as low psi as possible to give you the biggest footprint for traction and flotation.
Once stuck be prepared to dig. Actually, be prepared to dig before you leave your house. Extra shovels, traction ramps, a few good pieces of cardboard can make it easier for you to lay on as you shovel and can even be shoved under a tire in an emergency.
Bring a buddy. One that has some experience where you are headed. Being able to 'read' the sand to know where is safe and where you'll sink is handy. Bungie ropes can save you hours of digging. If you are foolish and go with only 1 vehicle be sure you know how to dig in an anchor with the spare tire, or one of those shovel self extraction devices.
Be sure others know where you are and when to worry.
And a few supplies incase you end up staying overnight from that 'quick' beach run down the other end of the sand.