There are a couple of reasons why big baits are usually more productive in the fall. First, the days are getting shorter and the water temperatures are going down. This seems to signal to the fish that it's time to put some fat on. The fish seem to prefer to eat one large meal instead of several smaller ones. It requires less energy for them to eat once than it does for them to catch several small meals.
Also, the baitfish that were spawned in the spring are at a larger size now, and some baitfish that are fall spawners are more accessible to the predator fish now. It seems that the larger predator fish are more interested in eating the size baitfish that are more abundant now.
If you can't get redtails, suckers will work also. I like to start with a minnow in the four to six inch range. If the bite is on, go bigger and you'll get bigger bites.
If you're looking specifically for walleyes, a redtail on a Fire-Ball jig is tough to beat.
If you're after largemouth, and if you can fish a spinnerbait in the range where the bass are calling home, use a spinnerbait with a big blade, and add a PowerBait or Gulp! trailer to bulk it up even more.
If the bass are deeper or want a slower moving bait, employ a Jungle Jig with a big trailer, something like a seven inch Power Worm or Gulp! Super Worm. If you're in big fish water and your goal is the biggest bass you've ever caught, try a ten inch Power Worm on a Texas Rig. You won't get as many bites as you would with a smaller worm, but when you do get bit, hang on.
When you're fishing in the fall, the chance for catching a big one is good. Don't take chances: Make sure you're using fresh line.
Autumn is a great time to be on the water, and if you use big bait, you have the opportunity for a truly memorable fishing experience. Find that out for yourself in the next few weeks.