I found a piece of wire in my food I want to take action. What do I do to start?
First of all you did not indicate if you suffered any physical injury from the wire. Since it was not mentioned I will assume that you did not.
In a lawsuit of this type for there to be liability there must be legal fault. Without that there can be no obligation for someone to pay damages. Additionally, there must also be some type of injury suffered. Yes there was a defective product - the wire in the food. But what was the harm done? Absent physical injury/illness or medical costs, it is unlikely that you could recover enough money to make a lawsuit worthwhile. You could try to argue "emotional distress" but this is very hard to prove, especially in this type of situation.
However, you could consult with a personal injury attorney just the same; these type of consultations typically are free. What you may have better luck with is by contacting the restaurant (if this is where this happened) or the manufacture or seller of the food. See if you could get some type of compensation from them. No business wants bad PR, most especially in today's economy. Just make sure to keep the wire and the can it came from.
A product is defective if it is not in the condition for ordinary use or is unreasonably dangerous. In this case, a piece of wire can be extremely harmful to you if you were to ingest it. The wire is not supposed to be in the food as a matter of common sense and practicality. Was the wire found in a can of food? was if found in a plate served at a restaurant? In any event, you need to document this occurrence and take a picture. You also want to keep the wire in a bag. You should take this to a lawyer. You need to explain where you were and where the food came from so that the lawyer knows who to go after for compensation. Most lawyers will meet with you for free the initial time, so do not hesitate here as you likely have about 2-3 years tops to file this lawsuit in court.
Were you injured. That is the first and most important issue. Lawsuits are designed first and foremost to compensate people for their injuries and costs. If you were lucky enough to not be injured, you do not have anything to sue for. (Just finding a piece of wire doesn't lead to a viable lawsuit.) Indeed, even if you suffered minor injuries (say a cut lip or cut on the inside of your mouth) and minor costs (a doctor's visit), it would not be worthwhile suing.
Also, even if you were injured seriously, if you don't have good evidence that there was wire in the food and that it caused your injury, you would have difficulty recovering. At a minimum, you hopefully still have the wire and the food. A medical report or witnesses corroborating your story would be very helpful, too. If you don't have evidence, then bringing a suit based only you own assertion of what happened would be challenging.
You can certainly consult with a personal injury or products liabilty attorny--many will provide a free initial consultation. But unless there is more than what you write, you probably do not have a case.