Welcome to DV. =D

Like others have already said, a MILD during a WBTB period is usually the easiest for beginners. As for nightmares, when I want to wake up during one of mine, I close my eyes, think of my physical body lying in bed, then I start kicking my legs a bit. It also helps if you keep telling yourself to wake up. Alternatively, you can also spin around on the spot. Doing so usually changes the dreamscape but you might lose lucidity if you don't keep reminding yourself that you're dreaming while you spin.