I don't think we can get students to plan their own lessons. But we can motivate them to discover and experiment with language on their own. This could be researching a topic before or after a lesson, looking on the Internet for self-study materials, or purchasing ESL books and CDs.
In the classroom, it's not so hard for students to discover the target language without the teacher spoon-feeding the information. For example, if your lesson is on the simple past tense, explain and provide some examples for the /-t/, /-d/, and /-id/ sounds. You can then arrange students in pairs, distribute a worksheet with twenty key verbs, and have the students arrange the verbs accordingly. Students are using what you have just presented, using knowledge from past lessons, and thinking about the language together. Of course, if you don't present the target language, or ask students to figure out language above their level, then the activity becomes frustrating rather than an opportunity for discovery.
Heads Up English - Materials based on current events. Just print, and teach!