Make sure to delete an Action Plan once your page ranks, so you can free up a slot in your Action Plan allotment for a new keyword. In order to delete an Action Plan, you need to be on the My Actions page, and viewing a single Action Plan. Select the Action Plan URL from the drop-down menu, and then click on the keyword (if you have more than one Action Plan for that URL). Once you're on the page with only one Action Plan active, you'll see a link to "Delete this Action Plan":
Clicking the "Delete this Action Plan" link, and clicking OK in the confirmation dialogue box that pops up, will delete that Action Plan and all of the associated Action Recommendations.