This will help you set up a FOWLR. I have posted product recommendations, type of lighting that should be used, and the fish for the tank.
Step 1: Buy a filter.
This isn't something I can get detailed on, but I do recommend either a bio-wheel, or a sump. I can't get into product descriptions as I don't know much about this. I'm sure the other members will fill me in. :)
Step 2: Fill tank
After you set up the tank in a place where you want it, you need to add the sand, and fill with dechlorinated water.
Step 3: Add salt and Live rock
I use Seachem Reef salt, but you can use any aquarium salt you want, just don't mix brands, and don't use table or rock salt. Now that you have filled the tank, pour in the salt and run a powerhead and the filters for about 4 days. After you finish getting the salt mixed, you may add your live rock.
Step 4: Wait
You need to wait at least 2 weeks before adding fish, test the water weekly. Once the ammonia and nitrites are at zero, and you are showing nitrates, (nitrates should be below 40ppm) then your tank should be cycled.
Step 5: Buy a light.
For the best results, you might want to get a metal halide, but since that is a very expensive light, I would recommend either a T-5 florescent, or a power compact fixture. I bought a Current USA orbit fixture, but I would recommend the Coralife Aqualight for power compact, and the Nova Extreme for T-5 lighting. The bulbs you will need for the Coralife Aqualight are 2 50/50 6700K bulbs. (should be included) Bulbs for the Nova Extreme should be 1 10,000k daylight, and 1 460nm antic. (They are included in the saltwater model.)
Step 6: Add your first fish
At this point you can add 1-3 damsels. I got 2 Fiji blue devil, and 1 sapphire damsel. Then do a 25% water change.
Step 7: Wait
You now should wait at least a week before adding more fish.
Step 8: Add more fish
You can add 4 fish off the list below, or anything other members say are able to live in a 55 gallon aquarium. Then do a 25% water change.
Ocellaris Clownfish (multiples ok)
Firefish (only 1)
Neon Blue or Gold Goby (multiples ok)
Step 9: Wait
Wait at least 1 week.
Step 10: Add final fish
You can now add you final fish, I will let members recommend so there are alot more options.
Always do a 25% water change once a month at minimum, always check the board for advise, not you lfs. Fish at your lfs may be small when you buy, but some 2" fish at your lfs will become a 1' monster, so do you research before buying fish.