There is an important distinction to be made, in the new environment and with the plugin changes we have made, between claiming land and protecting land. Claiming land is largely unchanged. Short version: put a marker (wall, fence, etc.) around it until you build on it. Don't claim more than you plan to use. Don't claim right next to someone else unless they are ok with it. The exception is around build spawn, where we encourage people to build close together. Protecting your land/chests/whatever is done with the new Grief Prevention plugin (the golden shovel). There will be a wiki entry explaining this plugin further. In the meantime, if you have any questions ask. Yes, this also refers to claims, which may be confusing, but they are two different things.