New base is actually pretty simple
For me it's buy a new device. I like my gadgets and new ones are fun, so for me it's awesome. For those less free with their loot you erase everything on your device and completely start over. Not so fun as getting a totally brand spankin new toy, but works like a charm.
One of my sons decided he wanted to start a second account and so he wiped my iPad. My account is linked to Game Center so I just log him out and log me in. It's really pretty simple. The only really hard part is getting my iPad back! I'm thinking COC has taught him that thievery is good.....