THE ONE INCH PER GALLON RULE IS A MYTH!
It works for small fish, but once you get to bigger fish, say 3" plus, this rule no longer applies. The rule has to due with how much bi-product the fish give off. Clearly, a 4" fish like a Rosy Barb, give off way more ammonia than a 4 - 1" fish. If you get all small fish, under 2", then the rule is fine. Still don' beleive me? Would you put a 40" fish in a 40 gallon tank? I wouldn't even put an 10" in a 40 gallon tank on it's own. Just have to displell this myth.
To start, decorate you tank however you want, wioth everything but fish. Do fishless cycling of the tank. A google search will tell you about this. letting a tank "sit" for 3 weeks does nothing. You need to monitor chemical balances in the tank daily while adding pure ammonia (ammonia bought at hte grocery store is fine, just make sure it is 100% ammonia). Get a chemical test kit that measires ammonia, ph, nitrite and nitrate. "The big four"
As for fish, there is one 'friendly" kind of algae eater, but it's name escapes me right now. You LFS(local fish store) probably wouldn't have it anyways. When I was looking for fish locally, they were notto be found anywhere.
Other adivce. Do not buy from chains! The people there don't know anything. Only buy from mom 'n' pop shops. They tend to know more and take better care of their fish, meaning you'll get healthier fish.
Also, when choosing fish, make sure they are healthy. learn about things like ick and fin rot. Two common problems. Don't buy fish in the same tank as these.
Feeding: Only feed your fish what they can eat in three minutes. Feed once or twice a day. Once you've had them a while, you can leave them for 7-10 days with out feeding them. They'll be fine.
When you start stocking your tank, do not get all the fish all at once. maybe start with a pleco and a small school. Then add more, maybe weekly for a month till it's stocked. This will allow for the tanks biological filter to adjust to the increasing load over time.
Algae eaters: Algae eaters like the slime on the bodies of other fish. The slime is a protective coat, so the algae eaters essentially kill other fish. If you get them, you have to be careful to get other fish that are comaptable.
Filtering. There is no such thing as too much filtering. When in dobut, spend the extra $5 for that bigger filter.
While fishless cycling is occuring, now is a good time to go to the store and look at fish. Let us know what you want to get.
PM me if you need more help. I'm an aquarist, not the best, but it is a hobby of mine. Other people here also seem knowledgable.
I suggest you start with a Pleco and a school of about 6 tetras. What ever you like visually. Move on from there.