Hike (or bike) hills, rugged ones if possible, and gradually build up mileage and pack weight. If you have hilly trails nearby, ramp up your miles and elevation on them. If not, you’ll find stair climbing and descending is really good preparation. Work toward more. Strengthen your ankles, legs, butt and back. Get them ready for their key involvement on the CT. If you don’t have access to hilly trails or good stairs, stair climbers and related machines also have value. Keep moving.
At the same time, train your feet and dial-in your footwear. Try for a combination of shoes, socks and insoles that do not give you blisters. Make refinements before you go and spend more money if you need to. Because blisters probably end more CT trips than anything else, your advanced work with your footwear will pay off.
If you can, go on an overnight (or multiday) excursion and check out all your gear. (Hit the backcountry if you can but, if you can’t, do it in the back yard and especially when the weather is bad.) Learn what you can leave behind and what needs changing. Lighten your load. Tweak things. Repeat on additional overnights if you can.
Altitude presents a different training challenge. If you have high mountains nearby, try for excursions there knowing that each outing prepares your body a little more. But many of you aren’t near any high elevation terrain and there’s probably little you can do in advance. Consider a careful start to your trip as being highly worthwhile; it can minimize your risks. Read our recommendations on this site: https://coloradotrail.org/traveling-the-ct/altitude/.
Enjoy your training as part of your trip and have a wonderful adventure on The Colorado Trail.