Steve,
That 'someone' told you correctly for the most part. It
certainly
isn't the most exacting explanation for an antenna, but it will
get
you into the 'ball park'!
The length of an antenna has to be such that it provides
enough
signal to your receiver so that it (the desired signal) is
louder
than the noise. For most HF signals, 33 feet will be plenty.
Of
course, 'more' would be 'better' in some cases, but not always.
The
one thing that will do more to increase what you hear is
height. Get
the antenna as high as possible (sort of like you standing on
your
'tip toes' to see farther, right?). You also can only work with
what
you have, so if ceiling height is the most you have, then use
it.
The 'shape' of your antenna also can play an important part
in what
you hear. If the antenna is high enough above ground, it can
become
directional in nature. I wouldn't worry about that too much,
though,
just be aware of it. Stringing your antenna out as long and as
straight
as you can make it is much better than wadding it up into a ball
and
throwing it into a corner. There's also nothing that says that
you
can't change the 'shape' of the antenna, if you want to see what
would
happen.
The size of the wire used isn't going to make a lot of
difference,
as long as it is strong enough to support it's own weight. Make
it
ea$y on your $elf, co$t wi$e. The length isn't really that
critical
so you don't need to use a micrometer to measure the length of
your
antenna. A little more, or a little less isn't going to make a
big
difference. A foot or two is meaningless, twice the length is
"more
better", sort of.
Probably more important than anything else is how the wire is
connected
to your receiver. Use the proper connector, if possible. If it
isn't
possible, just make sure you don't short out the receiver's
antenna
terminals. Won't harm the receiver, you just won't hear much.
SWL'ing is fun, so have lots of it!
'Doc

PS - That's about as non-technical as you can make an
explanation of
a complex subject. There are 'exceptions' to everything I
said,
but what I said will certainly work for you. Knowing 'why'
it
'works' is interesting, but not really necessary to make it
'work'.
The 'having fun' is the important part...