Pretty much the best key to awareness is to make sure you’re always asking where you are, what you are doing and if it makes sense. On top of that, try to feel the world around you. Since you’ve had a lucid dream before, ask yourself if it feels the same. Now, even if you think it feels right, it’s not a gaurantee, but it will help keep you thinking.
On top of that, I highly suggest you read this article by Robert Waggoner. He gives a lot of good insight into what frequent lucid dreamers keep on thier minds.