I went to trainer and he showed me a device called the "pro-stretch". You can get a single or double for both feet at same time. I prefer the single as it fits in the bag better.
It's a heave molded plastic with flat top and guide for your heel. The bottom is round (half circle). Stand next to door frame, wall - whatever - and stand on device. Slowly rotate forward and hold - back and hold. repeat several times. Since I started using this I have had zero problems with shins, calves, achilles etc.
They are not cheap - cost about $50 but well worth it. I got mine from alimed.
ProStretch® Products