Set the XStart and ZStart values to whatever your desired start point is. That point will be the corner of your overall area. Set the BlockSize to the desire size of the area for each user. The default is 500 (1/2 kilometer on a side) which should be more than sufficient for individuals.
The only thing you'll need to enter here are your players' names (in the purple area);the rest of this worksheet generates itself.
When done, copy the cells in the Cuboid Protection String (blue area) into protectedCuboids.txt and the Warp Point Strings (green area) into warps.txt
The final product represents a 20 x 20 boxes that are each 500 blocks on a side.
Each person will have a warp point "theirnameArea" and an associated area that is protected for just their use.
The blocks go from bedrock to stratosphere (0 to 127). The warp points are at 110 altitude (Y Value) which should prevent most folks from popping into solid mass.
Warping to these new points the first time often causes my server to crash. I think it is from the requirement to generate so much new terrain all at once. After each one is generated the first time, I can warp back to it fine.
My recommendation would be to "pre-generate the areas" by warping to them yourself during a maintenance window.
If anyone has any questions or suggestions, please don't hesitate to offer them. This is just one technique. I still have public build areas on my server, but this way every person also has a large place to call their own.
Jerick - Check in the Minecraft Servers and Server Administration forum categories. There are numerous threads explaining how to setup a server. Also, Google Hey0 forums to find his support forums which are also extremely useful.