To create a smooth, even base for your backsplash, you'll need to scrape off any texture and patch any holes or cracks with spackling compound. Once you've done that, sand down the area with medium-grit sandpaper and vacuum up the dust. To ensure all grease and oils are gone, you can use either TSP or an ammonia-based cleanser to wipe down the wall. Now all that's left is to start installing your beautiful new backsplash.