I’ve had a few questions about how I wired up my serial console on my Pi, so here’s a quick post about it.
The best place to start is the page on elinux.org that details the pins on the GPIO header (RPi low-level peripherals). You’ll notice you need pins 8 and 10 for the Pi’s TX and RX pins, you’ll also need a ground point which you can find on pin 6. You can then hook those straight into a 3.3V USB to serial converter’s GND, RX and TX pins and get a console running. Note that you need to connect the TX pins to the RX pins or you won’t be getting any output. Do not use a 5V cable. Do not connect the power pin on the FTDI adapter to any of the Pi’s power pins either.
If you don’t have a compatible cable you can take a look on the Console Access wiki page for my PolyController project, the serial cables it uses are all compatible with the Raspberry Pi. The most important thing to get right when looking for one of these is that the IO pins are designed for 3.3V TTL levels and not 5V or RS-232’s +/- 12V or you may fry your Pi.
Those IC hooks you see in the picture are from Proto-PIC: IC Hook with Pigtail.
Once you have your cable connected up, set up your favourite terminal to connect at 115.2Kbps, 8n1, no flow control. Hit enter a few times and you should get a login prompt if your image is configured correctly – the official Debian image as well as my Debian Wheezy image both are (the others probably too, but I haven’t tested them).