Sure, you can spend a lot of money on fancy sand carving tools - we will be happy to sell you some at the Sons of the Beach Online Shop, as a matter of fact! But we are not afraid to tell you that there are a lot of common items -- things that you probably already have laying around the house in junk drawers, etc. -- that will do a fine job of carving sand.
For example, old kitchen knives, putty knives (paint scrapers) and trowels of various sizes and shapes all work very well for carving sand and are readily available. Steak knives with the point broken off will make good basic shapers and can also be used for scooping out doors and windows. A steak knife with the point still intact can be used to etch out surface detail like bricks and rocks or even lettering.
Don't throw away those rusty old paintbrushes! The soft-bristled ones are the best - excellent for getting rid of loose sand or unsightly knife marks.
The photo below features a bunch of items that I found at a local "Dollar" Store. All of these items cost $3.00 or less and they all can be used to carve a better sandcastle.
So mess around with these for a while -- and then when you are ready to get serious, let us fix you up with the good stuff.