Go to the hardware store and ask a sales person to show you the sheet metal screws. You only need about 10 per shoe. I find that 3/8-inch length are best. They're long enough to stay securely in the shoe, yet if you want to remove the shoes later, they're easier to get out. You obviously wouldn't want a screw that is so long that it punctures through the sole of the shoe and into the footbed—ouch! I've only experimented with screws on the perimeter of the sole of the shoe. I would worry about a screw under the ball of the foot or big toe, even though I agree with those who advocate for a neutral (i.e. flat) foot landing, yet the screws on the perimeter seem to do the trick. If you're a heel striker, you can put two or three screws in the part of the shoe where you strike (just look for the area that is worn on the shoe).
That's it. Screw shoes are fantastic when you're out on an easy run on snow. Personally I love those easy runs where you don't see anyone outside; you feel good about the fact that you're getting your run in even though it's cold outside.
Screw shoes are great for easier, slower running. I've never done any faster running in them, and I would worry about slipping and falling (which is such a concern for me given my coaching experience—I've had runners who fell once, and had to alter their training for the next six weeks).
When it comes to winter workouts, I love fartleks this time of year. Why? Because you can just play with pace. If you're indoors, you can simply get down to your threshold pace and run it for a few minutes, then back off to a pace that is faster than your easy pace, but still slow enough that you recover a bit. My college track coach called this pace "steady." Then you repeat it—faster running followed by steady running. I like to just go by feel and say, "For 50 minutes I'm just going to play with pace." Fartlek is a Swedish term that means "speed-play," and I assign it for athletes because I want them to learn where their aerobic threshold is by playing with pace.
But if you're someone who needs more structure, you can do a workout where you run five-minute blocks of time. You can run two minutes at your threshold pace, then back off for three minutes, then repeat. We call that "two minutes on, three minutes steady."
Or you can do three on, two minutes steady, which is obviously a bit more challenging. Or you can do four minutes on and just one minute steady, which is a workout I like to use once I think someone is fit and ready to start racing. That minute is so short that your heart rate doesn't come down much (assuming you're running steady and not easy), but it does give you a mental break between the four-minute segments. Because the workout consists of five-minute blocks, you simply figure out how many minutes you want to run—30 minutes, 40 minutes, 50 minutes—and do the corresponding number of blocks (so 6, 8 or 10). With a short warm-up and short cooldown, you can get a great stimulus in a short amount of time.
Finally, there are two simple things you can do in the winter to ensure that you are ready to train hard and race well in the spring. First, you need to conserve some mental energy in the winter. If you can't stand the cold and can't stand another day on the treadmill, then cross-train or do some general strength and mobility. No big deal. You won't lose fitness. And that one-day break will probably give you the motivation to get back after it the next day.
The second thing is very simple. It's so easy to become a night owl in the winter when the sun goes down so early. Resist that lifestyle and go to bed on time, or even a bit earlier than you normally do. The winter is a great time to catch up on your sleep, regenerate and recover. The intensity of your running will probably be lower in the winter months, yet you still want to rest to stave off both injury and illness. So get your rest and don't stay up watching television.
Best of luck this winter. The cold, snow and ice will eventually end, but in the meantime, train smart so that you an train even better when the weather warms.race.