Make a plan:
First you should make a basic plan on what type of design or shape that you are going to build your sand castle. Remember to keep it simple as the more complicated you make it, the harder it will be to build. If your kids are going to help you with the construction, then be sure to have sections where they can do whatever they want to add their own unique features to the sand castle.
Find a good location:
If you are making your sand castle on the beach then try to find a nice location that is slightly away from the crowds. You do not want people running in to your sand castle and knocking it over repeatedly. Also, try to build your sand castle away from the water as the waves can flood your construction area and cause a lot of damage.
Have a decent sand wedge:
Make sure that you have a decent sand wedge that you can use to help build your sand castle. This will definitely help you speed up the process of building your sand castle. You should also get a bucket and some other small tools like a shovel to help you out.
Use wet or damp sand:
When you start to build your sand castle, use your sand wedge to help level out some nice wet or damp sand. This will essentially be the base of your sand castle, so make sure that you compact the sand to give it some strength. Make sure that the sand is not too wet otherwise it will collapse from the weight.
Start to build your sand castle upwards by layering more sand on top of the base that you created earlier. Use your hands to smooth the walls of the sand castle to make them strong and look nice. Remember not to build too high as the weight of the sand can collapse on to itself.