My, kelp, if you aren't subtle!

Welcome to DV Basically, as Kelp said, just relax. If you need to swallow, scratch an itch, or if there's something that's bugging you, just address it and continue to fall asleep. Otherwise, all you'll be doing is thinking about what's making you uncomfortable.

As for what else kills lucid dreaming, stress is a big one in general. If you're really stressed out, you won't sleep very soundly and chances are your recall will go down the tube. Also, alcohol and depressants can case you to sleep more soundly and can shorten the amount of REM sleep that you get. So, if you do drink, just keep that in mind.