Let's clear up a popular misconception before we begin: Lucid dreaming is not the same as astral traveling/projection.
Results may take up to one week. Rest assured that If you put in the work, you'll see results, sooner or later.
Make a habit to look at the back of your hand every couple of hours. Ask yourself, 'am I dreaming right now?', look around your surroundings and carefully observe before you answer the question; look at the wall, the details of the furniture, and the people around you; make mental notes on why it is not a dream, for instance - your hand isn't blurry, all your stuff are in the exact place they belong, there's no floating furniture, etc. Repeat this exercises every day. Eventually, you'll reach the stage where you are going to be asking yourself these exact same questions in your dreams, and when that happens, you'll be able to easily identify that you are not in the waking state. That's it, you now know how to lucid dream!
Q: What to do if I encounter a seemingly evil spirit in my dream?
A: Say, 'In the name of the creator of this Universe, I command you to go away'. That's it, the entity will vanish.
90% of the time I’am able to tell myself that I’m dreaming, but obtaining control is very hard. When I do obtain it I get excited and loose control, and on rare occasions I’m able to have a full blown experience. I will try your watch method, hopefully it works better than the other methods I’ve tried.