If you have been sitting still for a while, move around or exercise your feet to warm them up. Stand on your tiptoes and then the flats of your feet or stretch your feet out and point your toes, then bring your feet back in and bend your toes. Repeat these till your feet feel tingly and warm. Get up and walk around. The movement will circulate the blood in your body and warm them up. You can even do jumping jacks or run in place to really get your blood pumping. Sit down on a chair or the edge of your bed, with your legs dangling. Swing your legs backward and forward at least 30-50 times. This will get your blood flowing to your feet more. Do this with your whole leg, including your thigh. Make powerful movements! Swing your leg as wide as possible. Rub some foot cream or lotion onto your bare feet and massage it in. Rub your toes, heels, and the soles of your feet. This helps circulation and makes your feet feel warmer. Then, put on some thick socks or shoes and slippers to keep the heat in. Use a warming cream like Nutrasal or ProNeema for an extra warming boost.

TL;DR in Vietnamese:
Di chuyển và tập luyện cho đôi chân. Thực hiện động tác đá chân 30-50 lần. Mát xa chân.