What are some things that students can pass on to younger students, or to those at lower levels? Take some of those ideas and make videos with them. You don't need fancy equipment, and the video quality doesn't have to be very high; just using a smart phone will work. If you don't have access to even those, the students can make posters instead. This project works best in primary and secondary schools, but you could find a way to adapt it in other environments. Students can do this project in groups of two or three.
Identify a Problem
Have your students answer one of the following questions:
What's something you wish you knew before you started this class/grade?
What's something many people (in your school) don't know, but should know?
If you could tell your younger selves something, what would it be?
What's something you can do well now that you couldn't do very well a couple years ago?
The answers to these can be academic, social, or personal. Students should probably come up with a few answers, then pick the best one later.
You may want to take this time to review the Unreal Mood, such as with wishes and regrets or with conditionals (3rd for past).
After they've brainstormed, each group will need to choose one topic that they would like to share with younger students and that involves more than a single-sentence response.
Craft Your Advice
Next, the groups should write out the advice they'd like to give in a paragraph or two. When read out loud, it should take 15-30 seconds.
Some advice might be more instructional, so you can review how to lay out steps, including using conjunctions and adverbs of sequence, using imperatives, or using modal verbs of obligation. Other advice might be more like persuasion, so review how to express reasons (using 'because', 'so', 'therefore', etc.) or how to disagree with opposing viewpoints. Others still might be more hypothetical (either considering how things might turn out well, or considering how things might go poorly without this advice), so review hypothetical structures like 1st or 2nd conditionals.
Students should structure it like a small essay. What's the best way to introduce the topic? Maybe with a question they wondered themselves a few years back? Then place the details in the middle, and finish with a conclusion: what's the most important thing you want people to remember?
Shoot the Video
Once students have finished their scripts, their groups should film their advice. They'll need to decide which group members say which parts. Have them practice reading the script aloud before they film. And once filming begins, the students should look into the camera as they speak, as if looking directly at whoever will be watching the videos later.
Keep in mind this isn't an exercise in performance (unless you the teacher want it to be), so their 'stage presence' doesn't matter much; just get them to speak clearly enough in a tone they're comfortable with.
Once each group has finished, compile the videos. Show them first to the rest of the class. Do other students agree with their classmates' advice? Then, when everything is ready, give the compiled videos to the teachers of lower grades; or wait for a special occasion or until the end of the year; or save them for the first day of next year's class.