Crop your pictures. You might want to leave some perfect pictures uncropped, but others you will need to trim. You can crop your photos in interesting shapes, such as circles, stars or diamonds, or you can simply crop them in basic rectangle or square shapes. Consider cropping some photos very close to isolate the subject. Vary your cropping technique to add visual interest to the collage.
Arrange your cropped photographs on a large sheet of brightly colored card stock or poster board. Before you paste the photos, try out a variety of arrangements. Take pictures of each arrangement with a digital camera so you can compare them. Then, once you have chosen an arrangement that works particularly well, you can refer back to the photograph so you can recreate it. Try arranging your photographs in an orderly pattern or in a free-form, overlapping design. Consider arranging your photographs on a piece of card stock or poster board in the shape of a star, cat, moon or flower.
Paste your photos on the poster board or card stock in your pre-planned arrangement. Use acid-free, photo-safe rubber cement or paste. Complete the photo collage by adding personal notes, sketches or watercolors, and add mementos such as concert or travel tickets or newspaper clippings.