A few tips:
Start with a bucket of a ton of ice and just a bit of water at the bottom. Put your pump at the bottom of the bucket, obviously. For the first 15 minutes or so (for a 5 gallon batch), don't recirculate your coolant water to the bucket with ice. You'll just melt all that precious ice. Recirculate to another bucket. As you're doing this for the first 15 minutes or so just replenish the little bit of water in your ice bucket. After that time, start recirculating to the ice bucket.
Make sure you have a decent pump. I use a March 809. Another good model is a Little Giant 4-hc-md.
Pinch the end of the return copper pipe. I think Jamil mentions this. It should help a little in creating that nice whirlpool.
The way I have mine set up, I have the return pipe returning to the top, inside of the chiller. I've timed it and that seems to chill it the quickest.