The main rule for writing an essay on any topic is to get the title right first. In this case you are to write an essay on friendship. Straightaway there are so many topics under this main heading. Twenty possibilities are listed below. But the key to your success is to find the topic or slant or angle on the topic which best suits you.
Ask yourself these questions. Do I like the topic? Do I have any personal stories about this topic I could write about? Is the topic I like so popular that many other students have already written about it?
You want to try and be unique. That gives you an edge because the person marking your work will not have to wade through an essay which has been written a million times before. Look at the following and see if one or more really appeal. Sometimes an essay which almost appeals can be used in a brainstorming session to get the perfect essay title.