1. Write a letter they enjoy. Outright humor doesn't work in a cover letter. It generally can't be pulled off. It falls down because someone is always the butt of the joke, and in an interview situation you don't want that person to be either you or the recruiter. Rather than telling jokes, connect to the hiring manager in a light hearted way. Try _ "I was hopping from project to project so often I thought my legs had springs." Then make the connection to the reader. "I'll bet you can relate to that." And finally, segue to the value you can add. "I tried a lot of remedies until we finally developed a scheduling system that actually created more productivity and less useless movement. I'd be happy to tell you how we did it and see if something like that would be valuable for you."
2. Main Body _ This is the most important part of your cover letter and may be made up of one or two paragraphs. This is where you state your key competencies and relevant experiences that have the most impact on the available role. Try to focus on those competencies that will be beneficial to the company if they give you a chance. Clearly state in your cover letter how these can be used to successfully carry out the tasks of the job. Draw their attention to how your previous achievements and roles can help you perform the job well. It is critical that by reading this part of the cover letter, the employer is convinced that you are suited for the position.