Caring for Wallpaper and Paint

Hello! My name is Darren and I'm from a place called Liverpool which is in the UK. Last year, I spent a couple of weeks painting and wallpapering the interior of my home. However, I was really disappointed to discover that after a few months the wallpaper had begun to peel away from the wall and the paint had started to flake away from the wooden fixtures. I called my friend Dave who is a professional painter and decorator and he explained that I hadn't been caring for the paint and wallpaper properly. He gave me some great advice which I will share with you here.