What are some good ways to attract and keep duck (mainly wood ducks) in my ponds during the off season?

Nest boxes. Too late to put them up for this year's hatch.

What about feeders or possibly planting? Will putting a corn feeder in a shallow area work? Whats good to plant for woodies?

Since it's a migratory bird, they may not come back.

I know of guys with catfish ponds that will drain them, plant some jap millet, then fill the pond back up before the season.

I guess all ducks are migratory, but I think a good percentage of them are local birds. I feel like I read close to 50%.

Let me first disclose that I know nothing about duck hunting. However, a business contact who was an avid duck hunter once said that he would pour molasses in his duck ponds. Apparently the ducks would fly home with the smell of the molasses on them which would in-turn, cause more ducks to follow them back the next year. Sounds simple, and could even be deemed illegal or even unethical according to one's personal opinion. Just sharing what he told me.

Sounds like a tall tale...

The molasses thing is something that I've heard folks talk about before. I think this was always in the context of hunting wood ducks though. By pouring out molasses where they feed they end up with it on their feathers when they go back to roost at night the other ducks pick up the scent/taste from it and follow them to feed int he morning.

As for ducks that actually "migrate..." the 50% thing MIGHT be of some truth to wood ducks because we have lots of resident wood ducks in Alabama. As for other species...teal, gadwall, shovelers, red heads...they nearly ALL migrate from the prairies. You're only going to see them while the are migrating south in the winter and again in the spring when they are headed back north.

All about the imprint!!! Corn, corn and more corn! If you have a private hole that has a few ducks on it corn the heck out of it right after the season. Spread it in all the shallow spots you can find. If you can have a flock stay in there for a month or so after season they will imprint on the area and most likely return the following year looking to follow the yellow brick road again, that is if they don't just stay around year round! Get you a couple nest boxes up right after the season too and that will also leave an imprint on them! It will definitely take about 20 years, but plant you some oak trees close to the edge of your pond. The overhanging limbs will drop acorns right in the pond. My brother in law has a good little swamp/pond that gets a good bit of woodies and the oak trees planted there are about 10 years to young to produce acorns, but hey it will be worth it once they are dropping food directly into the water! Also, if you can get the woodies dumping in there regularly the big ducks in the area will eventually follow to see where they are feeding. Its a long slow drawn out process to get it just right but you have to start somewhere!