Have a definite idea in mind. One might be "How do others see me?" vs "How do I see myself?" Another could be "The world as it is" vs "The world as I would like it to be."
Make two piles, one having to do with the first question, one having to do with the second. Raid files, magazines, drawings, photocopies, printmaking papers, poems, your diary, maps, photos, extremely thin, flat and dry leaves or flowers for items to place in the two piles.
Think of how you might enlarge some of the items or reduce some of the others. Scan or photocopy accordingly.
Plan out where you will place the various items by using two papers the same size as your panels. These are your trial sheets. Know where things will go before you paste.
Use your support as your background.
Cut items out. In case of mishaps, have more than one copy of each.
Mark off 1/4 inch all around on the panels if you plan to frame them. Trace around the items on the panels lightly so you do not lose track of where they will go.
Number the items on your trial sheet if there are a large number. Avoid numbering the actual items. You don't want anything showing through.
Brush matte medium on the backs of the items and also on their places on the panels and glue them down. Matte medium is an excellent adhesive as well as a medium for acrylic paint. You can overlap things to some extent.
Be careful not to let the medium dry out on the brushes.
Place waxed paper or freezer paper over the panels and cover them with heavy books. If you are using freezer paper, place the waxy side down to rest against the collage items. Leave overnight. Rough edges can be smoothed over with more matte medium.