Something nifty I just recently discovered was I can build a fence on top of wood walls. That kept the stupid greydwarves out and let me grow my turnips in peace. I also built portals all around the inside just because I like fast travel, and my portals are completely safe now, at least on the fort side. If ever want to expand it, all it'll take it building a workbench or two. Works great, though it's in the Meadows. I didn't want trolls coming by.