The adapter you can buy off da ebay for couple of euros, something like this thing is very good, I've got several of the critters.

There's really 2 ways to access the serial port pins when debugging an N9; the quick&dirty way and the good way.

The quick&dirty way is to just hold a pinheader in place against the gold contacts under simcard tray with your hand when booting... Sounds odd but it really works
I have done it more than once, it is good for Rx only, to get a log what happens in the device.

The good way is to make an adapter, I have done that by cutting a piece of plastic card and sandwitching the gold-fingers off a broken simcard adapter between the cards with glue.
It comes out as surprisingly good contact, good for both Rx and Tx so you can log into the console.