How big is your pond? How much lower is your downstream than your pond?

I've used everything from 1/2" garden hose to 8" pvc as siphon. Heck, I've even used quarter inch rubber tubing to siphon / drain my baby's bath tub. If your pond isn't too big, 2" pvc is a good solution. Connect enough 20 foot sections so that the pond end sticks out into deeper water in the pond and the downstream end is as much lower as practical. I usually use a gasoline powered water pump connected to a water hose with a clog buster http://www.plumbingsupply.com/clogbusters.html which screws on the end of the hose and is inserted into the downstream end of the pipe. Then you start up the pump (or turn on the faucet). The rubber piece expands to seal the pipe and the running water fills the pipe from bottom up. It is actually fun to watch the water progress up the pipe (starts sagging), over the dam and into the pond. Doing so also helps you watch for leaks that could let air in and stop the siphon. Sometimes (virtually always) the pipe in the pond tries to float as the air from below is pushed through it. Sometimes I push it down a bit. Sometimes I don't and it eventually sinks. Ideally, it would all sink so that no air is left in the pipe (you should see lots of bubbles coming out). As long as you have enough pipe and enough drop, you can get by with some trapped air in it. When you're fairly confident the pipe is as full of water as you can get it, you just turn off the pump (or faucet). The rubber clog buster contracts, the weight of the water forces it out of the pipe, and your siphon is flowing.

[Linked Image from i108.photobucket.com]