The question I get asked the most is "how did you do that" and my answer is "sand and water my friend, sand and water". This instructable was made to elaborate on that with a few tips I have learned over the years.

Supplies

Sand - Everyone says their sand is the best, but unless you are bringing your own. You will have to use what is there. Sand with clay in it does pack better, but basically just try to keep debris out of your sculpture.
Water - Get it any way you can, buckets or dig a hole until you hit water. Speaking of buckets, add a piece of pvc pipe to the handle of your five gallon bucket for a much nicer feel.
Shovel - Anything will do, but light weight and rust proof are key features.
Forms - To get height you need a form. Buckets of different sizes with the bottom cut out or a large trash can work well. Wooden forms and plastic roles are what the pro's use.
Carving tools - Most anything will do, I have used a plastic fork and spoon while on vacation. Besides my hands the tools I usual use are;

-Offset square nose spatula

-Pointed and straight metal trough with brightly painted handles so I don't lose them.

-Tube/straw for blowing away sand. Got to have this one.

-Straight piece of plastic wood with ruler drawn on it.

-Dusting brush, furniture sliders and spray bottle.

-I'm not affiliated with them, but I won a set of tools from CanYouDigIt. and have used them ever since.

Step 1: Setup

Grab all of your tools(in a cart if you can) and head to the beach.

Pick your spot carefully, consider the tides and sun direction. Most sculptures take hours of work and you don't want it washed away too soon or bad shadows from the sunset. The three minions picture shows a moat that had to be dug quickly before the waves took my sculpture.

Step 2: Pound Up

A lot of people just shovel up a large volcano, and put water in the middle and in holes on the sides. This works and depending on your design might be all you need.

If you want to go big. Take your form of choice and shovel a few inches of sand in. Then add water and mix the sand and water leaving no dry sand. Repeat this process until finished, with some tamping of the sand along the way. I step right in there like I'm crushing grapes to make wine.

When you are all done, carefully remove your forms. For buckets and bins, I like to hit the sides a few times loosening the water seal before pulling them off. For forms, I slowly remove them and try to smooth the sand to avoid collapse. Hopefully you made sure it was straight during initial set up.

Hand stacking is another great way to build up. Put sand and water in a bucket or a hole and with two hands scoop out a big mound of very wet sand. Plop it down and shake/form as needed. It's like making runny pancakes. Repeat until desired height is reached. Watch this and all the videos from SandCastleLessons.com for some great sand castle building instructions.

Step 3: Carving

Now the fun part begins. Always start from the top and working your way down. Rough out your design with a large trough and remember to step back occasionally to give yourself a better view. This process just takes time and practice. I use sketches and my phone as reference material when creating.

I'm an amateur, but here are some tips I can share

Never undercut more than 45 degrees.
Always carve in from the sides, never pushing out. This prevents blow outs.
Mix textures. Rough sand next to smooth and deep cuts to use shadows.
Mist with water to keep the top layer from drying out and blowing away your detail.
Always make your sculpture wider at the bottom.
Wear sunscreen.

Learn from your failures. The last picture is a recent contest sculpture that fell an hour before judging. It was too heavy and I undercut too far. It happens.

Step 4: Finishing Touches

Before you start taking pictures of your master piece. Clean up any rough edges with a small dusting brush and smooth as much as possible with the furniture sliders. Finish with either smoothing or roughing up the sand a few feet around the sculpture to give it that professional look. Don't forget to sign your work, (I 3d printed a mold with my logo).

If you would like to see a few more things I've made over the years. Here is my website and I encourage you to look online for more videos and sand sculpting websites.

This instructable is entered in the sculpt and carve challenge, so if you like my work please give it a vote. Thank you