Dear Jennifer;
        I didn't notice a lot of replies to your heartfelt queery, so will
chime in with my 2 pence worth, based upon my experiences here in New
Scotland.
        First, collect mainly on the very lowest of tides- it is quite
surprising how many species are found just below the low water level-
the "sub-tidal" zone.  Wade right in, and a face mask would come in
handy for this.  Second, forget about sandy beaches, which are good
mainly for collecting shells washed up after a large storm, but which
support rather few spp of their own.  The best places to look are areas
where there are rocks in sand or other seds- look under the rocks, and
on the underside, and the sides of rocks- differents spp will tend to be
found  associated with large and small rocks.  The same applies to old,
saturated driftwood, to a certain degree.  Third, look in all the
habitats you can find in a given area- look in cracks and crannies,
brackish water sediments, at the base of, and on seaweeds and
sea-grasses, near the high-watermark for pulmonates, check out kelp or
other seaweed holdfasts which wash ashore, etc.- the more habitats you
search, the more spp you will encounter!!!  Fourth- sift fine seds of
the silty and muddy sort (low water and subtidal especially), using a
1mm screen if you can, since there are many spp, some very tiny, which
live in fine sediments.  You can make a small screen to carry to the
shore, or bring back bags of the muck, to where you have a source of
running water to make sifting easier.  Look closely for the little ones-
some are devilishly difficult to see!!.  Fifth and finally for now, do
not forget tidal pools- one never knows what one will find in these
little pieces of the sea left behind when the tide goes out!!!  Again,
search every crook and nanny, and you will be rewarded for your
diligence.  Often, small shells will congregate around stones when the
tide retreats (in pools and elsewhere.  I found some neat things this
way in Scotland once- like those cute little Trivia you have over
there!!), and it pays to look through this material carefully.
 
        A word of caution- be careful to disturb the habitat any more than is
absolutely nessessary!!  Replace any rocks you turn over (ESPECIALLY the
larger ones, which support entire communities underneath, much of which
which will quickly die if left exposed!!), do not rip up seaweeds, and
in general, leave as few traces of your prescence as possible.  It may
be said that our impact as collectors is minor in comparison to
developers, industry, dune-buggies (ecological dissasters on
wheels!!!!), etc., but we are ultimately responsible only for
ourselves.  (also, in order to get the best collecting in, you will be
seeking out the least disturbed places, so as to find the highest degree
of diversity).
 
        Good luck, and i would be delighted to hear how your more successful
trips go!!
 
                                                                                                                                        -Ross of the North.