Tips on breaking in brand new tall boots?

stick on the largest socks you can fit in them, too!
Find a stair and place the balls of your foot at the edge to where your heel hangs off the side, then sink far into your heels like you would while riding. I did this motion up and down holding for a few seconds at a time for about 10 minutes each day. It's also a great calf workout!
DER DAU BOOT STRETCH SPRAY we use this on all the boots we sell to customers at Dover
Wear them while you're bathing horses, and walk up lots of stairs
Wear them everywhere. Shopping, work, etc. I wore nmine to Barnes & Noble
Condition them so they become more supple(especially around the ankle). wear them around the house before riding, wrap your ankles in vet wrap to avoid blisters once you start riding, use a moleskin if you do get a blister. As a last resort you can get them professionally stretched my a cobber.
The easiest way i found was to wear them lots around your house and the barn and to ride in them but make sure to clean them well before showing in them