Switch from satin or silk bed sheets to cotton. Satin feels slippery to the touch and increases the chance of the blanket sliding off of the bed.
Tuck the edges of the blanket between the foot of the mattress and the box spring. Secure bedsheets are less likely to move around and reduces the amount of work required to straighten up the bedding in the morning. Tuck the edge of the blanket underneath the side of the mattress opposite of your sleep spot.
Clip one end of a bed suspender to the bottom edge of the blanket and tuck the edge into the bottom of the bed. Clip the remaining end to the perpendicular side of the blanket to fasten the suspenders. The suspender keep the blanket in place and are easily removable.
Insert a blanket support between the mattress and box spring, and place the blanket over the device. A blanket support is a metal device that elevates the blanket and keeps it off of your feet. The device is typically used in hospitals and nursing homes to keep the feet cool while sleeping.