I agree that autosuggestion as you're falling asleep works best. Really be clear when you tell yourself that you will remember all your dreams.

Also try to set your intention to wake up after every REM cycle to record your last dream. If you really want vivid recall, it is best to remember ever dream right after it happens. This means waking up in the middle of the night to write down notes.

When you wake up (no matter what time of night it is) lay still for a few seconds with your eyes closed while you try to remember what just happened.