1. I think that the theory is that if, during the day, you look at your watch or read something around you and it is strange, odd, or wrong, then you are dreaming. Obviously, in the waking world you will not be but the habit should eventually carry over to the dream world, and you will find that your dream self should look at it's watch which may trigger an LD.
Note: This has never worked properly for me, but many others have reported that this technique or one similar works.
2. In LDs when you have little control, it is common to think things like 'Hey, if this was a nightmare, there would be something behind that curtain. What the..? Oh, sh-'
But, with practice, it is easier to ignore those thoughts and concentrate on happier ones. Of course, with a really high level of control, there is no reason to be afriad of nightmare situations, and many dreamers use them effectively for theraputic (Heh) purposes.