Start off the essay with a funny joke or amusing anecdote that relates to the overall topic. This will set the tone for the rest of the piece and it will put your reader or audience in a light-hearted, cordial mood. For the sake of good taste, keep the humor appropriate for the assignment or occasion.
Structure the information that you are trying to convey so that it is concise and thoughtful. Use short sentences and conversational words, and pay close attention to the tone of the essay. The friendlier it is, the easier it will be for readers to digest. Decide on a focus for the essay, and plan to use only information that contributes to the focus. Revise, making sure every part of the essay contributes to the theme and projects friendliness.
Finish the essay with an engaging statement or personal incident that demonstrates companionship. For example, you could share a favorite quote on friendship or tell a story about how you met a close friend. If you decide to close the essay with either of these components, note that it will be this portion that readers remember most.