If i go to bed tired, and fall asleep quickly, i always remember my dreams. I also tell myself that i'm going to remember them, and that i'm going to write them down when i wake up.
This morning, i woke up, remembered a dream, spoke on the phone, went back to sleep and had another dream, and still remembered the first one!
Not often i can do that, the new dream usually cancels out the old one.
If i go to bed before i'm tired, and lie there tossing and turning, i don't usually remember my dreams.