Easy to follow video:
Regions can be a maximum //size of 100,000 blocks.
//wand //pos1 //pos2 //size /rg claim <region-name> /myregions /rg addmember <region-name> <player-name> /rg removemember <region-name> <player-name>
Region flags are also available to users rank  and up:
/rg flag <region-name> <flag-name> [value]
mob-spawning entity-item-frame-destroy entity-painting-destroy creeper-explosion enderman-grief chest-access pistons use sleep vehicle-place vehicle-destroy water-flow lava-flow snow-fall snow-melt ice-form ice-melt mushroom-growth leaf-decay grass-growth mycelium-spread vine-growth soil-dry greeting farewell weather-lock
Less easy to follow word tutorial (Also old):
The first command, //wand, gives you the tool to define a region in space. You need to define a three dimensional region. Start at the Top-Left-Back, and end at the Bottom-Right-Front. This may seem confusing, but there’s a well written wiki page available. Note that Users only have access to the SELECTION, not the world changing tools. This also includes the //expand command, and in fact, anything with the worldedit.selection.* permissions, here. There’s a complete list of the commands you can use here. You have a limit of 5 claims in total, ever. You also have a limit of 100,000 blocks per region. When you select both corners, you can use the command ‘//size’, and that will tell you how big your region is. If it’s too big, you’ll need to shrink it.
After you’ve selected your region, you can claim it. You use the command /region claim regionname
The ‘claimname’ needs to be a server-unique name. Try to describe your area there. Something like /region claim robs-awesome-house will set ownership of the region I’d selected to myself, and call it ‘robs-awesome-house’.
You cannot change a region once you’ve made it. You can only delete it (/region delete regionname) and re-create it.
Make sure you’re happy with the area you’re selecting before you claim it. Admins will delete your region, demote you back to user, and possibly ban you from the server if we think your region is placed in somewhere that will annoy anyone. Yes. We’re bastards.
Adding users to your region
After you’ve selected and claimed your region, by default no-one else can alter that region. You can grant other people access to the region with the command:
/region addmember regionname username
If you want to remove that person from your region, you can use:
/region removemember regionname username
You also have access to most of the flags mentioned here. Note that some are disabled at the server level, such as TNT and Lava flow. A handy one is a welome and leaving message. If you want people to get the message ‘This is Rob’s area. Watch for Creepers’ when they enter your region, you can set the greeting flag:
/region flag regionname flag greeting This is Rob’s area. Watch for Creepers
The server will then say ‘Flag set’.
Ask in IRC or Mumble for more information, if you get stuck. If you talk in chat about not being able to select regions, you’ll probably get muted, and you’ll quite likely get tempbanned.
To ease people who can’t seem to google, here’s a couple of Videos of how to do it.