Alternatively, shoot wider a bit, then correct the tilt in post. You should always try to make sure it's as straight as possible while shooting, but don't waste too much time doing that. The more time you spend trying to make your camera perfectly level, the less time you have to think about other elements of the shot (composition, lighting etc)
Also when using a tripod, get your composition right before you set it up. Otherwise it's very easy to get distracted and leave the camera in the same spot for a long time and get only one composition. I did this many times before and only realised my mistake when I got home.
