oh god, lol I'm glad you brought up this question before attempting it. It took me forever to figure out a good way to do it.
anyways, get a 5 gallon bucket and fill it up about 1/3 of the way with sand then grab a hose, turn it on pretty high and then try to wedge it down into the bottom....when the bucket over flows it should rinse out the fine particles and the bigger ones should stay in the bucket, or atleast most of them... stir occasionally with the hose and then once you see the water running clear add more sand. Once you have as much as you think you need inside of the bucket you'll want to rinse for a while longer after the water has cleared up to make sure you got almost everything.
Or, atleast that's how i did it
there are tons of methods out there