First of all find out how much time you have. This will tell you how much research you will have time to share, obviously. Knowing the time limit will also allow you to decide how much material to gather for each point.
Do anticipate audience questions and try to find the information you need to answer those questions. Depending on the speech you can either weave that information into your remarks or handouts, or use this research in the Q&A part of the speech.
Do rely on good sources. Even if you are trying to prove a point, that GMO foods are dangerous for example, use sources the audience will find credible. Any book or Web site promoting fringe science, conspiracies, or alternative medicine is probably best avoided.
Research always need to suit the audience. Your teen audience doesn't want to hear about a bunch of scientific studies. Your fellow managers don't want to know what bloggers and science educators think about the company's area of research.
Good online sources include: