Note what ideas you're trying to convey about getting good grades in college. Are you trying to explain that having good grades will get students further in their chosen career? That having good grades will help students earn a higher lifetime income than those who don't have good grades? That having good grades will earn the respect of peers, professors and mentors alike? Write down a list of what you're trying to convey on a scratch sheet of paper.
Plan your presentation. If you're using visual aids to interpret what you're saying, its important to know what you're saying first so you'll know what type of visual aid to create. Decide which specific points during your presentation you'd reinforce with visuals.
Find images that convey your presentation points. Choose pictures of students smiling, students studying individually and together, confident candidates during job interviews, and happy couples with nice houses and happy, playful children. If you're showing statistics in your visual aid, find a font size and type for your numbers that suits you. Use colored pie charts and graphs to make the numbers stand out. You might also choose images to show what happens if students don't get good grades, such as unhappy workers in low-level jobs or a tired couple arguing. If you're familiar with the students to whom you'll be showing the presentation, have them pose for some of your pictures.
Acquire your medium. Are you mounting the visual aids on a poster board, or projecting a Power Point presentation? Prepare your pictures for the medium you're using. Organize your visuals neatly in the order they'll be seen.
Practice a dry run. Gather together a group of people you rely on for providing honest feedback. Show them your presentation; introduce the visual aids at the appropriate time. Ask for thoughts and/or constructive criticism. Make the necessary changes.