BarbMazz,
i am bacteria'd/creatured out right now

plus i am leaving to Washington D.C. for the next 5 days today

.....
football day today with some postings during commercials

.....after that
so i will link you up instead

for now anyway

will get into stuff like placing rock on the sand bed and the effects on a DSB and stuff another day.
Bob Fenner and Anthony Calfo give good intros, its not indepth or anything but good reads to get you started on sand. here is a article from each on sandbeds. something to chew on.
LiveSand DeepSandBeds
basically a DSB is a modified "Jaubert system"-same idea but no plenum- OO and talk about a topic of big debate, plenums are right up there. i think alot of the concerns with a DSB and debates originated from plenum debates. so it might help knowing about that system before getting into variations. esp sence its not much of a variation.
here is a good article about it.
Advanced Aquarist Feature Article
then there is this old thread here i found with a good decision on DSB, its a good read~
DSB...Let's Discuss!
FYI; i too am setting up a clam tank right now

and will be using a DSB. something i know you have not got into yet is the chemistry and feeding of clams, a properly set up DSB goes well with a clam tank.