If you're alone and are choking by yourself and have no help you should first call 911 immediately when you begin choking if possible.
Then as you call 911 start doing abdominal thrusts on yourself.
The abdominal thrusts can usually remove the food or whatever it is that is lodged in your throat.
You can also do the Heimlich Maneuver on yourself by using your fist, a chair, pole, table etc.
To perform the Heimlich Maneuver on yourself start by making a fist and placing it on your abdomen between your navel and your ribcage.
Then, hold your fist with your other hand and drive it inward and upward, using a j-shaped motion.
Repeat this multiple times until the food is dislodged.