So first, gather up some paper lunch sacks, or better yet, buy a bottle of wine and save the brown paper sleeve that you carry it home it. Anything much thinner than this will not hold up well through the process. Cut the bag open at the seam, discard the seam and the bottom of the bag.
Now mix up some white glue and warm water until the glue dissolves. I'd say about 4 parts water to 1 part glue, but I'm not sure it's that important. Take your bag and crumple it up into a ball and submerge it in the glue/water. Remove, squeeze, open and crumple again to repeat the proceedure. Twice is fine, do it a third time if you want extra wrinkles AND if your paper is holding up well. Open up the bag and place it on top of a protected surface (I put it on top of a plastic trash bag so it doesn't stick).
Next take acrylic paint (I use craft paint at this stage) and paint your wet paper bag. Paint it however you'd like. You don't need a thick coat of paint, a little goes a long way. Think about the colors you want to end up with.
Once your paper has dried, iron it front and back (between pressing cloths or parchment). This will seal in the wrinkles and make it easy to work with.
Finally, I like to dry brush accent colors on top to highlight the wrinkles. On this piece I started with the yellow (craft paint) and then added silver metallic highlights with Lumiere. If you want to, you can put a glossy acrylic glaze over the whole thing when you're done.
I hope you get a chance to try this. It's a lot of fun!