Default timestamp value

As a precursor to this question, I read:

CREATE TABLE
Date/Time Types (and corresponding input/output)
Date/Time Functions

...but I still don't see how to have the default value of a timestamp to be
the time at which the individual record is inserted. I just get the time I
created the table. Specifically, what to put where the '?' is at.

... "TimeDate" TIMESTAMP DEFAULT ? ...

I tried 'now' and 'current' but it just makes the default value the time
when I create the table, and 'current' gives me the word 'current' back in
psql, so I imagine I'm not taking that in quite the right way =) I can see
why it does this for both of these, althought in the docs, it says current
is current time, deferred, but I dunno what that means.

Any help or pointers to a nice resource? IMHO, the PG docs are a great
reference, but not much in the way of terrific examples =)

- r