Make a list of memories of your parents that are important to you. It doesn't matter how big or small, or the order. Write them as you remember them. You should find a quiet place and work on the list for about an hour.
Take your notes, and choose what should go in your tribute. You also have the option to write a separate tribute for each parent. Decide which memories to focus on, and write more detail about why they are special to you and what emotions they evoke.
Organize this information into a rough draft. This does not need to be perfectly written. The main goal is to write the information in the order you wish to present it and to provide yourself with a guide to your final draft.
Write the formal tribute. Include an introduction, which basically outlines how much your parents mean to you. Follow that with as many paragraphs as you need to complete your tribute.
Write your conclusion. It should summarize how your parents have influenced your life and how much your relationship with them means to you.