First off Welcome to AA.com .... by far the best informational site out there
! Don't trust a word your LFS
will tell you, if you have any doubts come here and ask first!
First thing you wanna do is start here ...
Filtration - For Biological filtration For a 33 gallon tank your looking at about 70lbs of Live Rock (more is better) and probably around 60 some pounds of sand ... that is if your looking for a nice DSB
! you could also get some mechanical filtration i.e. HOB
filter or a canister style filter, or sump/wet-dry filter if you want the best!
Flow and circulation - Look at getting some Maxi-Jet Powerheads, probably 2 1200's should be good for you tank as I'm not real sure on dimensions of the tank!
Lighting - I read you want some corals and such? Depending on what specie of coral your looking at PC
lighting for lower end corals and MH
lighting for your SPS
and Clams. This is the most confusing part of the SW
and requires a lot of research and knowing exactly where your going with your tank! Different corals have different lighting requirements so research what you want and then ask for more help.
For anything else .... you'll need SW
test kits, Refractometer for measuring salinity (spend the extra money and stay away from hydrometer), cleaning tools i.e. mag float glass squegee (not sponge from the grocery store) and what has been real handy for me a couple wooden skewers that I use to move things around or flip overturned snails .... which brings me too
Snails and crabs and shrimp ... you say you don't want any in your tank, but trust me they are vital to have! Turbo Snails will eat the algea on your glass and Nassarius snails will sift your sand. Hermit Crabs will consume leftover food particles and also help with algea control. Shrimp depending on type are beneficial as well, Skunk Cleaner Shrimp will help keep your fish clean from parasites and also do a great job of scavenging for leftover food. You'll need them ... don't skimp on them!
I think I may have forgot some stuff but if you read through the articles provided in the link I gave you that should also help and always ask more questions!!!
Good Luck and enjoy the hobby ... it is truly rewarding!