Yesterday night Thirst, with the help of Rigor Mortis & Da Meanest an' Greenest, took back the T4 keep "Ironskin Skar" in Black Crag from the filthy hands of Order. I did not participate personally, but will use this as an example how to claim a keep and what it costs. Before you can claim a keep, of course first you have to conquer it. So gather a strong warband and find one occupied by the forces of Order, preferably already claimed by an Order guild. ;)
You can check which realm owns a keep by looking at the mouse-over window. It will also show if a guild, in this example Thirst, has claimed that keep. So after you conquered the keep and slaughtered all the NPCs (including the Keep Lord of course) in there, you can claim the "empty" keep. If you just leave it, NPCs from your realm will repopulate the keep by themselves. If you want to claim the keep (Note: Your guild needs rank 14 to be able to claim) for your guild, after the fight you'll have to head to the top of the structure. IF you are a standard bearer for your guild, you'll be able to interact with one of the banner poles on top and you can place your banner there, claiming the keep.
It's important to note: The claiming standard bearer won't be able to carry a standard as long as the guild keeps that keep, because he "uses" his to claim it. Once your guild claimed the keep (your guild can only have one keep claimed at a time), the banners will transform into your guild heraldry, showing colors, patterns and emblem depending on your guild rank. In addition the Keep Lord will be hired by your guild and will show the guild tag as well.
But of course such service does not come for free. If you intend to claim keeps, you better fill up your war chest in advance with gold. The costs for keep maintenance are:
T3 Keep Maintenance = 6 gold/hour (144g per day)
T4 Keep Maintenance = 10 gold/hour (240g per day)
Maybe a good idea to talk about guild tithes & taxes or how guild members donate money in advance. We did not really plan for the keep claiming and had to realize our funds inside the guild vault were not enough to hold it for long. Next time then... ;)
So you wonder what the benefits are for paying maintenance and defending a claimed keep? Well, should someone attack "your" keep you'll get a warning in chat - so better make your way over quick when that happens. The benfits of a claimed keep include, that your guild banner tactics (the ones "equipped" in the banner used to claim) will be applied to the specified RvR area for ALL realm members to benefit from. In addition your guild will earn experience over time while holding the Keep. If a Keep (that is claimed by a guild) is captured, then the Standard associated with the Keep is considered captured.