Roads tend to get beaten "clean" in ruts, especially in the southlands. Drive in those ruts, there's better traction there. Just slow down until you feel no hint of fishtail instability, and then another 5 or 10 mph slower. It's that simple.
Your enemy is bridges and big culverts. These tend to accumulate more and slicker ice, and they ice-up first. The sand (if any) helps only for a little while, then the wetted sand and slush re-freezes into a new and harder coating that is just as slick as plain ice, and a whole lot harder to pound loose by the passage of traffic. Never, ever assume a bridge is safe! Turn your flasher on to warn the folks behind you, that you are doing something they don't expect, and slow way down before you reach the bridge. Most cars have a maximum controllable speed on slick ice in the neighborhood of 20 mph. You need to be moving at least that slow as you reach the bridge, so you can see what's really on it, in time to respond. Plain and simple.
If the bridge has clean ruts or is clean and dry, speed back up and cross. Stay within the ruts. If the bridge is icy, stay under that 20 mph. Steer to cross the bridge in a straight line, get off the gas and brake (and stay off them) and make no steering changes while you coast across. You will come out just fine on the other side, if you do these things. You will not come out fine, if you accelerate, brake, or turn, in the slightest. For long bridges, modify this as absolutely-constant speed driving, no braking, no turning, at substantially less than 20 mph. I recommend about 10-15 mph for most cars.
For roads with paved shoulders, there is usually gravel on the shoulder and a few inches beyond. If you start fishtailing before you can slow, put two wheels into that grass and gravel right at the edge of the shoulder. Your fishtailing will stop. But, don't stay there, decelerate by coasting, and put it back onto the road, before you get stuck. Don't do this on a farm-to-market road, there are no shoulders, and the ground off the pavement is generally too soft (because of the precipitation). Just drive much slower on those roads, so that you never fishtail.
Pickup trucks and front-engine, rear-drive cars are extremely prone to rear-end-breakaway skids, because the weight distribution is very bad for all-wheel traction. You need to go much slower than a ordinary car, because once it breaks away, you are out of control, and you won't get it back until you come pretty much to rest (which might entail fetching up against something really solid). It'll warn you by feeling very unsteady, by wanting to fishtail. Find the fishtail speed for your vehicle (not in traffic, please!), and then drop at least 10 mph below that. Be aware that this speed changes as conditions change.
SUV's are famous for being able to "go" when other vehicles won't, especially the 4-wheel-drive ones. But, they do not stop any better than the worst of the conventional cars, and they are far more unstable due to the high center of gravity. I've seen more SUV's upside down in medians and bar ditches, than any other type of vehicle. Slow way down!
The vehicles with more even weight distributions front-to-back can suffer from the other type of skid: front end breakaway. That's when you crank the steering wheel to turn and nothing happens. Why? You are going too fast. Steer straight and miss the turn, coast down, and drive a lot slower. The problem will go away if you slow down. If this happens on a curve, the only thing you can try is a shallower turn. Do not brake (you will spin out), do not accelerate (same result). Very gentle steering inputs will sometimes work when a big input fails. Trouble is, most of the time, you don't have room for that. So, I recommend you try your vehicle out turning on the ice in an empty parking lot. Look for the speed at which it breaks away, and back off at least 10 mph below that. Use that reduced speed figure as your maneuvering speed out there on the icy road.
Some folks put chains on. They work, but rarely are they rated for driving more than 10 or 15 mph. You can pretty much do just as well without them, at those low speeds. Drive too fast, and they come apart. The flying fragments are steel shrapnel. They will damage your car, and they will hurt innocent bystanders. I haven't owned chains in decades. No need.
Don't forget to turn on your lights. This is as much to be seen by others, as it is for you to see better. In the fog, mist, and snow, all colors are "stealth", even reds and yellows.
And don't forget to wear your seat belts. If you don't know what you're doing, or have little practice, driving on ice, chances are actually very high you will have at least a minor accident. Could easily be a major accident. Belts make the difference between a bruised ego and a hospital stay. Or death.
If you get stuck, and you can almost but not quite "rock" your way out using forward and reverse, then try using the vehicle's floor mats. Put one, textured rubber side up, under each drive wheel. For marginal cases, that's often just enough extra traction to get free. Better to get tire tread marks and dirt on your mats, than to freeze while waiting for rescue.
Finally, dress for it! Dress like you have to walk miles in the snow and wind and cold. You very well might have to.