If it is a finger, thumb, pinky, hand, arm, foot, leg, in some cases my rear has been asleep. WHATEVER THE CASE, this works.
Some people say just move it around. That helps, if you do it for an hour or so. BUT my way is to apply extreme non-injuring pain.
For fingers and hands:pull back dont stop when the feeling is back, stop when it hurts.
Arm or bottom: squeeze part closes to chest/abdomin/waist.
For foot, put it under the leg of a chair of which someone at least 3/4 of your weight is sitting on, most efficient if about 10 pounds over your weight.