If you remember something, a face, an action, even a feeling, it will often become a thread to pull back the dream. Have a notebook and pen ready to use beside the bed. Be sure the notebook is open to a fresh page and that the pen has ink in it. Go ahead and record the date. You might even want to write a sentence about today being the day you're going to start remembering your dreams.
Some people prefer to use a hand-held tape recorder.
But if you don't have these items on hard, go ahead and start with what you have. Then, when you waken and remember a dream, reach for the notebook and write it down. Don't be lured by the little voice that will say you don't need to write it - that you'll remember. Besides, you've told yourself that this is important. That was the objective, after all.