We use GriefPrevention on the SMP server; so to ensure you don't have your builds destroyed by other people you will want to claim the land!
You will start with the ability to claim 100 blocks, but this will increase by 100 blocks every hour that you are on the server. You can claim your land initially and expand it as your number of available blocks increase.
The area that you claim is from the build top to the build limit floor.
In order to claim, you first need a wooden shovel - to get that, simply do /kit and select the “Claim Tool” option.
To create a claim, simply take the claim tool, and click the first corner. It will appear as a diamond block. Go and repeat on the DIAGNAL OPPOSITE CORNER. The outline will now appear, with the corners marked with a combination of glowstone and gold blocks. This will disappear after a short time.
Please note, that claim areas must be a minimum of 100 blocks.
For a video guide, please see: [Fluffy Minecraft] How to claim land on our Minecraft SMP Server - YouTube
Claim Commands:
/Trust
/UnTrust
/ClaimsList
/AbandonClaim
/Claim
/ExtendClaim
/SubdivideClaims
/AccessTrust
/ContainerTrust
/PermissionTrust