Leadhead jigs and wintertime river walleye fishing go together like fresh fillets and beer batter. Being most efficient with leadhead jigs means paying attention to a few details.
Weight. Whether you're casting a jig from the river's bank, yo-yoing it vertically from a drifting boat or make pitch casts from an anchored position, a jig's weight often has a lot to do with how many bites you get, and how many walleyes your ultimately catch.
A good rule of thumb is to use as light a jig as you can while still maintaining a degree of feel of the bottom. I use a 1/4-ounce jig most of the time when vertically jigging in water of 10 to 25 feet. If depths exceed this it might be necessary to bump up to 3/8 ounce, particularly if it's windy. When casting up onto shallow flats, an eighth or 3/16 jig is often appropriate.
Hook Shank. Hook shank length depends on the type of dressing you're planning on using. When fishing a live or artificial minnow, I like to use a short shank jig like Northland's Fireball. The hook can be run down the minnow's mouth and back out behind its head, making a very compact presentation. The last couple of winters I've rigged Berkley Gulp Alive minnows this way — both 3-inch and 4-inch — with great results.
For presentations that call for a plastic body like a twister tail grub, go with the standard long-shank hook that most leadhead sport. Bass Pro Shops Painted Round Jighead is a good example of such a jig. The barbed collar holds the plastic dressing in place. A trick I've used for many years is to pinch off the tail of the twister, and then tip the jig with a fathead minnow. The body adds some bulk and color; the absence of the tail gives the minnow plenty of room.
Head Design. Round head and aspirin head jigs are great shapes for vertical jigging, as they offer little water resistance. They are also okay for casting, though a better option is a standup head. Bass Pro's XPS Walleye Jig, which features a moderate standup design, is a nice compromise for both casting and vertically jigging presentations.