How can I make a juicy (yummy) turkey burger patty?

Oprah used to rave about the recipe linked to below. Generally, as others have noted, the key is in adding moistness with sautéed or finely chopped vegetable/onions and cooking through without overcooking.
http://www.oprah.com/food/Mar-a-Lago-Turkey-Burger

Lots of great advice here. The bottom line is you have to either add moisture with apples, celery, onions, fennel or some other grated vegetable or you have to add fat like butter, bacon or cheese.

I usually add lots of olive oil!

I'm unconvinced that there is such a thing as a "good turkey burger". Let's face it, it's intended to mimic something else that tastes a lot better. Introducing fat (and frankly I don't think olive oil is a good one) is a good step. Turkey makes a better meat loaf than a burger for a great variety of reasons that go beyond seasoning. The meat for your basic ground beef burger is 80/20,meat to fat. So, where are you getting that other 20% from? And veggie burgers? Well those taste like they were made from papier mache.

Pouring about 1/3 cup of water at the bottom of a pan and putting at medium heat, covering the pan to steam once gray on top uncover letting the water evaporate then flip cook for another 3 minutes good to go

I add grated onion and garlic, as well as finely chopped fresh herbs (I like flat leaf parsley, chives, chervil). Not to forget salt and pepper! and I add an egg white for each pound of meat. That adds "juicy" and helps the meat hang together.

My favorite tricks 1) Cook down a peeled apple with a grated onion and some finely chopped celery for flavor and moisture and 2) A few teaspoons of homemade or Major Grey's Chutney.

I have a couple of things that I do - 1) add grated onion - it adds flavor and moisture and keeps it healthy and low-fat which I assume you are after. 2) add a tbs or so of olive oil - this adds "good" fat and flavor as well. Of course seasoning is key - depending on what sort of flavor profile you are after you can add a bit of other shredded veggie, herbs and spices. For a spicy version you might think about some minced chilis (fresh or canned) oh and roasted garlic would be great too!

You could render some fat from the wings, allow it to cool, then add it to the meat at a 70:30 ratio before grinding.