The things to look out for an understand are the cycling of a new tank and the filtration. It is overwhelmingly complicated sounding when you first read it (unless you understand chemicals, the periodic table, etc) but it really isn't.
Basically it's important to understand that in a river the fish get fresh water at all times, in a tank they do not. You have to use a combination of good bacteria and water changes to give them 'fresh' water. You should try to establish the good bacteria (cycling) before adding any fish and then get a regular time when you can do water changes and gravel vacuuming every week or so. The getting started forum should help a lot as the person above said.