if you have been working on an area that could use some improvement you might mention that strategy as part of your plan. For example, if you are in a field where presenting to groups is not a core skill but is somewhat valued, you might say "I plan to work on my presentation skills by taking a workshop on optimizing the use of presentation tools like PowerPoint. I have always gotten positive feedback about my presentations but would like to jazz them up a bit.
Try to incorporate some reference to a hot industry trend in your plan if possible. Review the latest journal articles and conference agendas for your professional associations and speak to well informed colleagues for ideas. For example, a hospital administrator might say "I have been reading articles on using electronic health records to generate clinical quality measures and plan to attend a seminar at the next Hospital Association conference on the topic."
The first step is to make sure you have a professional development plan at all times, since you never know when you will need to transition into job search mode. In most cases, this should include mastering the latest area of technology being tapped by employees in your sector. So a project manager might be prepared to say "I have been working on strengthening my business intelligence skills and have taken (or plan to take) a seminar on advanced Plex system ERP applications."