As the weather cools down, warming your horse up properly becomes even more important, and it starts in the stall. As they are outdoors less, your horse is not doing as much romping and rolling around getting dirty and stretching all those wonderful muscles. Begin by brushing your horse vigorously as if it is caked in mud from head to toe. Do the legs as well as you do the saddle area! This gets the blood circulating and starts to warm the muscles up. Take a tip from my dad and scratch your horse's belly and rump with a pitchfork!
This is a good time to brush up on your longeing skills or work in hand before you get on. If it's been a while for you and your horse, beware of assuming you can pick up where you left off. Start slow with some easy goals. Above all else, the horse must know "whoa" and "go."
Plenty of walk, as usual, is in order. Calm, forward, and straight. I often say the warm up is the ride. When you've had a great one, there isn't anything you can't try afterward.