The in's and out's will largely depend on the aircraft type, however the basics will be the same. On the A330, fuel is jettisoned from the inner wing tanks, and is pumped out by both the main and the standby pumps. It pumps at the rate of approximately 1000kg per minute. The jettison will stop at either a preset fuel remaining, or at a number of other points, which are detailed in the manual. The fuel exits via one of the inboard flap track fairings on each side. To get it to jettison, you follow the procedure in the manual, which simply involves 2 button-presses.
When dumping, it is important to be aware of your situation and to tell ATC. The A330 manual does not recommend dumping at less than 5000ft, to allow the fuel time to evaporate etc. ATC will route other aircraft away from you, to stop them becoming affected by your dumping. It is also unwise to jettison near to Cb's and it is unwise to dump while in a turn of more than 90 degrees - to avoid ingesting your own fuel trail - bad news!!
Hope this helps!!!
SLT
