From "Dream Dictionary" by Tony Crisp, Dell Books, Copyright 1990, IBSN
0-440-20861-0:

Remembering Dreams: Considering that each of us has four or five periods of
dreaming each night, most of our dreams are forgotten.  But for people who
observe family or friends regularly remembering a dream, and yet themselves
are seldom if ever able to recall one, the question arises as to why such a
wide divergence occurs.

There are many different reasons why dreams may be forgotten.  The most
obvious is that we do not give enough attention to our dreaming process.
When people become intrigued by what they might be dreaming, and develop a
motivation to remember, they frequently start recalling several dreams a
week.  From this standpoint, the reason why some people have always
remembered might be that they have always been either intrigued or anbxious
about their nightly dramas.

The way we rise in the morning has an effect upon this type of memory.  If
our attention is immediately turned outwards on waking, ther is little hope
of recalling a dream unless it has great power, as might a nightmare.
Spending a few moments leaving  our mind open to memory aids and recall.
Any visual, or even muscular activity, will fill conciousness with new and
powerful impressions which might obliterate the subtler impressions of
dreaming.  Rorschach suggested not opening the eyes and remaining physically
still.  Tests also showed that passage of time, even a few minutes, between
dreaming and attempting to remember causes many dreams to fragment and be
lost.  So any attempts to remember need one to record the dream quickly, by
speaking to one's bed mate, using a tape recorder by one's bed or writing it
down.

Some dreams have rather misty or fragmentary imagery and theme, while others
are clear, concise, and dynamic.  These latter are more easily remembered.
There may be times when we sleep with longer periods of wakefulness, perhaps
due to feeling cold, or uncomfortable in a strange bed, which cause dreams
occur in cycles during the night, if something wakes us during a dream cycle
the memory is easier, if only because less time has elapsed since
occurrence.  So another method of capturing a dream is to have one's alarm
gently sound prior to the time one usually wakes.  The last hour or so of
sleep includes a long period of dreaming, so waking in this period with
intent to remember can often capture the quarry.

There are also psychological reasons for forgetfulness.  Dreams often deal
with past areas of experience which we do not wish to remember, or would
rather not be aware of.  If we find it difficult to feel emotions, or feel
uncomfortable with them it is highly we repress dream memory, as dreams have
a base in high feelings.  Experiments have shown that during dreaming our
heartbeat, body movements and breathing frequently reflect intensified
emotions.  Also, research into what areas of the brain produce dreaming
suggest that dreams may be from the 'visceral brain', which is largely non
verbal.  If temperamentally we find feeling qualities a foreign language,
coonnecting with a dream would need to be a learnt skill.