Look for resources. Focus on using books, including encyclopedias. It's also a great idea to look up your planet on the Internet using websites like those listed in this Homework Helper to gather information for your report.
Decide how you will organize your report. You may begin with a title page and a short summary of the planet and then get more specific with information about the diameter, how many moons circle it, etc.
Double check your assignment to make sure that you have followed all of your teacher's guidelines. This is very important! Much of your grade depends on simply following the assignment directions. Make changes as needed.
Have a parent, or other adult, read your report and check for errors. You can also use spell check on the computer before printing out the final copy. Turn it in on time to get the best grade!