I thought I'd also put this in too. Once you know how, the process to get your tethered BBB running is slick and fast even for the beginner.
Don't read this if you are running the BBB with an HDMI monitor and keyboard. However if you are old waterfall guy like me and like your UN*X host with terminal access, keep reading. Connect a standard USB to miniUSB cable with the miniusb to the small connector on the underside of the board; it provides power as well.
BBB's IP is always 192.168.7.2 (serious, even with DHCP). Download PUTTY and pop in this IP address (make sure it is set to SSH) and connect. And you are live. Remember that UN*X is multitasking, so you can open up multiple PUTTY windows at the same time (same IP address and set up, but save each under a different name). This is helpful for reading man pages and the like while working on something else.
BBB has the Angstrom Debian-distribution of UN*X on it preloaded (I had a question about this when I saw the microSD slot didn't come with a card) complete with a nice selection of bins on it (like gcc, python and even man pages). It is locked, cocked and ready to rock.