Use a fine tip glue pen or tiny glue dots and place the adhesive behind printed letters or other darker printed elements on the transparency. I am a big fan of Glossy Accents by Ranger and tend to use this lot for transparencies and acrylic items.

Use adhesive such as photo tabs, double sided tape, liquid adhesive, etc if there is going to be an area of the transparency that will be covered by a photo or embellishment. Just be sure to apply your adhesive directly under the portion of the transparency or acrylic that will be covered.

Other popular ways to attach transparencies include brads, eyelets, snaps, clips, buttons, staples, photo turns, nail heads, and stitching.