Hi, I'm assuming you wish to save the fish when dredging the pond. First you will need a large container. I use a 50 gallon oval garden pond mold that you would use for a garden pond. Depending on the size of the pond and fish, you could just use a large tote. Just make sure it is rinsed out and has never had anything in it that may kill or hurt the fish. Put this somewhere flat and fill it with water from the pond. You will need a large air stone and an air pump. If you really want to be nice. Get some Aquarium salt and throw a hand full in. This will make the fishes temporary home like a Jacuzzi. Do not feed the fish while in this home. Put a netting over the top, but don't enclose it. Fish may attempt to jump.
Removing the fish from the pond. You will need two nets, or a fine net and something to direct them with. Lower the pond to 6-10 inches, they will be hard to see. Don't be surprised if there are more fish in there than you imagined. Use something that wont injure the fish to direct them into the net. As your draining water, listen for splashing, you will miss a few.
Don't leave the fish in their temporary home for more than a few days. Accumulate the fish back to the pond. Remember, if you have allot of fish, don't put them all back in, pick your favorites and donate or trade the rest. You don't want to overload the pond.

Hope this help, Craig