I'm a visual learner. So, I've found a lot of helpful demonstrations on youtube. Everything from computer repair to drywalling. Not sure if it would help, but here's a link to a search I put in: http://www.youtube.com/results?search_query=removing+back...
Also, you can guess what might be back there by the age of your house and the time period of any remodels that occurred after the original construction. Most of the walls in our house are paneling. Yuk. At some point, someone had added bathrooms. Plastic tile stuck with a serious, nasty glue directly onto plywood. Not awesome. We scraped off the tile and any glue we could and then used joint compound over the glue (to make the wall flat again), put on an oil primer and then put a glass tile backsplash onto that. Had it been paneling or drywall, we would have just riped it out and replaced it with fresh stuff (too much damage from the tile removal). The plywood was in good enough shape to allow our renovations without going deeper into the walls. We were also able to lay green bored directly onto the plywood, and then properly procure and tile over that for areas that were going to have more moisture.