The evidence you will need to present in court in order to win your lawsuit will depend on the particular circumstances of your case. In defective product liability lawsuits, however, claims generally consist of four basic elements.
First, you must prove that you have been injured or suffered some other kind of damage (almost injured doesn't count). Second, you must prove that the product involved in your case was somehow defective or lacked proper warnings or instructions. Third, you must prove that the defect (or lack of proper warnings or instructions) was the specific cause of your injuries or damages. Finally, you must prove that, when you were injured, you were using the injury-causing product more or less in the manner in which it was intended to be used. To learn more, read Nolo's article Proving a Defective Product Liability Claim.