without overexposing the hell out of the picture? I have tried several times, unsuccessfully. Please tell me the secrets. Thanks

in really bright light, you just simply won't be able to do it.

Or as Chupacabra mentioned - use a filter to cut down on the light (i.e.: polarizer filter).

Then set the exposure by metering off the brightest part, which usually is the water. Then from there, I'd adjust it down a stop perhaps to ensure things don't really get blown out and the exposure can be easily fixed in Photoshop as you can't fix a photo that's over-exposed.

You definetly need to use a tripod, 5-10 seconds exposure is great to achieve this effect. You could do a few seconds but it doesn't look as smooth as it could be like this one:

<img src="http://miketan.info/photos/albums/20040801_halton_falls/CRW_0947.sized.jpg">

This was basically in broad daylight but there was some coverage by the trees, and was shooting at the smallest possible aperature and the delay was maybe a second or two along with some blown highlights.

Followed by a tripod for long exposures.