A good eulogy doesn’t just tell the audience about the person – in a sense it brings the person to life in their imagination and gives them something by which to remember them. You can do this by telling stories about the person: the happy things, the funny things, the sad things, the unusual things that happened, which sum up their life. Talking about these and the enduring qualities which describe what they were really like as a person, will help you build a picture for the audience with your words.
You may have all the information you need, or you may want to speak to other people close to the person to get precise details and check your facts. You may have arranged the funeral as a friend of the deceased, not knowing too much about them and having no relatives to turn to for information, in which case you can base your eulogy on your impressions of them as a person. Once you have the material and have thought about it in relation to the people you are talking to, you are ready to start putting it together.