If you have accidentally ingested poison, it may be a good idea to make yourself sick. If someone else has ingested poison and they are not conscious, you should NEVER induce vomiting as the victim may choke.
Another important point is that you should NEVER induce vomiting in yourself or another person if the poison is corrosive. A corrosive is as dangerous coming up as it is going down.
Syrup of ipecac
Syrup of ipecac will cause vomiting and most people will be sick soon after consuming it. Make sure the person who has been poisoned is in a safe position -i.e. Kneeling and leaning forward or laying on their right hand side.
If no syrup of ipecac is available, soapy water can be be used in its place.
It should always be your priority to get medical attention when poison of any sort has been ingested.