I tried shooting sporting clays with dismal results. I a competent handgun shooter but don't have this 'lead' down right for shotguns. Any advice?

go pay for a lesson, money well spent...and practice all you can, at a point it becomes muscle memory, at least thats what they tell me, so I am not giving up yet

I have learned to shoot with both eyes open, looking at the target. Not sure if that is the proper way or not. I just know it has improved my percentages. Oh yeah, practice, practice, practice.

It is the proper way.

You might also want to try using an open choke to start with. Get that pattern wide so you can see when your starting to get on target then use tighter and tighter chokes till you're shooting a full and hitting everything. Just my .02. It's the same concept as sighting in a rifle without a bore sighter...kinda.

As a rifle and pistol instructor I can tell you one thing I do is focus on the front site as I teach in both rifle and handgun BIG no no for shotgun. Try focusing on the bird more than your site. I have to force myself to do that every time and if the bird get way out I go right to the front site like a rifle and miss every time..LOL

Head on Stock, Eye on Rock.

Cheek weld on stock and focus on the target...not the sight

yeah i think it is better to if ya focus on the target and use both eyes. when i started doing this i stared hitting way more
just my little ol two cents

Get some thing you can throw thru the air and a water hose with a tight pattern. Have some one throw it for you the different ways a skeet might fly and see how far ahead, up and down, ect you have to go to hit the target with the water.

First thing is to make sure the shotgun fits you. Close both eyes and mount the gun like you were going to shoot. Open your eyes and your dominate eye should be looking down the barrell. So when you concentrate on your bird the gun will be going where your eye is going. The gun becomes an extension of your pointing arm.

When I started shooting skeet, years ago, I was dismal. I took one lesson and bought a video by Ken Robertson (his son now runs the Elm Fork Range here in Dallas). In the video Ken explains things like gun position, eye postion, swing, lead, etc...It is an excellent tutorial and can be purchased at Cabela's or maybe used on Half.com

Good luck, good shooting.