isn't that what they are doing by asking here at an advice forum?
What equipment is needed will vary depending who you ask.
Basic are;
tank (obviously
)
substrate, 1-1.5 lbs per gallon of tank capacity
live rock, 1-1.5 lbs per gallon of tank capacity
heater
pump for sump
circulation pumps/powerheads
lighting
(may be the most $$$ of everything if you plan on keeping corals)
for filtration there are a few viable options.
most will recommend a sump setup employing a protein skimmer
but you can also choose to use HOB
(hang on back) type of filters or canister filters.
This is the area you need to devote some time and research to so you can determine what will be the most appropriate for your particular situation.
They all have their positive aspects and negative aspects.
The sump and skimmer solution is probably the widest employed and probably requires the least maintenance overall, but does require extra space to accommodate the sump and equipment that goes into it.
hope that helps