A Eulogy is a memorial speech for someone who has passed away. The one doing the Eulogy should realize that this is more than just a simple speech. Messing up the task of giving the Eulogy is like doing the deceased a disservice. A good Eulogy is meaningful, so don't overthink the process.
Considering the time constraints, you can still create a great Eulogy. There are also many
Eulogy example too. Just remember some ways to plan.
1. Summary of Achievements
Any person has a story to share about his or her life. Mention turning points in a person's life, like where he went to school and what made him want to pursue a career. Major turning points can be career decisions, traveling etc. Inspirational endeavors should be mentioned.
Make a list of the things you need to mention in your speech so that you don't forget them. Ask around if you don't know the details. It's ok to blow up the achievements of a person if it's a Eulogy. Remember what the Eulogy is for. You should aim to magnify the strong points and downplay the flaws.
2. Make Notes
Although your speech should flow and not be too robotic, you need notes. Use cue cards if necessary. Make sure your list is on paper and not just inside your head. In five seconds, you can forget all the things you memorized so you need your notes.
3. Time Your Speech
Some people either get carried away or become unable to talk when on stage. Practice your speech so that you know how long it is. Your goal is to mention everything on your list.
If writing out your thoughts is a way for you to come up with your speech, do it. Stick to what you planned and do minimal revisions.