From jk0...@acad.drake.edu:

Th'Elf can probably answer your question with more authority than
I can, since he has made a life's study.  Myself, I have known a
few, so I'll tell you what I have learned.

All of the elves I have known are less than 100% elf, having had
their elven blood intermingled with human blood during their ancestry.
The elven side of them seems to come out most noticeably when they
are children.  I suspect that 'human' is dominant over 'elf', but
that the human child state is most similar to the elven species.  
Consequently, a human child with true elf blood is most noticeably
'elflike' when young.

What to look for?  No distinguishing marks that I've ever heard of.
Slightly pointy ears can be one giveaway.  Long, thin limbs and a
tiny torso is another.  High forehead.  Big eyes.  Thin, curly,
wispy hair. A tendency to run and jump and prance a lot...to dream
and fantasize and sing in a high voice.  An odd combination of
helplessness and fierce independence.  Some human children with
elven blood may even exhibit magical powers.  I knew one who could
become invisible.

The elven human matures more slowly than the full human.  They may
remain small in stature or they may grow as large as an average-sized
human.  They pointy ears, so noticeable when they were children,
usually become more round like human ears yet they may continue to
protrude ever so slightly.  The ones I have known lost their magical
powers as they got older, but Th'Elf may know of others who have
not.  

Anyway, this has been my experience with elves.  Can anyone add
to this?

                                        ^V^  Baby Jinx  ^V^