Everyone needs to read the the 1G idle VFAQ. 2G owners need a little more information - as provided by Dirk Koenig (edited for presentation):
"Under the hood, in the middle of the firewall,near the top of the engine compartment, there is a bundle of wires. In this bundle you should find a brown plastic plug. Open this plug (pocketing the very important cap for later installation) and follow the VFAQ instructions for grounding.
For the inside plug, while sitting in the drivers seat, grab the corner of the dash where the center console and the underside of the dashboard meet. You should now be holding the diagnostic port in your hand. Get under the dash and take a look at the plug. There is a pink wire going into it. This is the wire you should ground, how you do it is up to you. (I shoved the probe from my voltmeter into it and grounded the other end)."
There is also now a VFAQ for 2G idle adjust - see here for details.