Dream walking, like Nim said is completely different. People can and do experience it by mistake. In essence you are following an energy link from an individual, into their subconscious mind as they sleep. A good way to test it would be to ask the person if they experienced a similar dream. Of course you have to remember it to do this xD
I would suggest focusing on the idea that you will remember. Do this before you sleep or attempt astral projection. Make sure to keep some form of journal handy at your side. This way you can write down everything you remember. Give yourself a moment to recall and jot down everything that comes to mind. After a while you will get better at recalling your dreams and experiences.