A lot has been discussed on meditation, and its effectiveness for achieving lucidness has been proved multiple times, either as a gateway to WILD or through Lucid living. You can search the forum for meditation, you’ll find something interesting in the archives.
As for he nightmares: with meditation comes knowledge of self, and with that your fears start to surface: When you get lucid in the nightmares, you must resolve to put an end with to the useless running from yourself. You can choose between two options: you can confront the monster directly, and affirm your superiority, eventually by battling (but this is rarely the case), or you can take the friendly approach, and start asking questions.
“Who are you?”
“Why are you tormenting me?”
“What can i do to win my fears?”
“Can you help me?”
“Can I help you?”
That, or a big hug, regardless of who’s in front of you, usually works 
. Some people have some nice adventure, after that, with what the nightmare trasforms into, usually.
The main point is accepting fears as a natural part of yourself and learning to know them, not to be driven mindlessly by them, but using them when necessary instead.