In my opinion rickyr is our resident water expert, being a water chemist for the EPA. I don't particularly care about my water parameters, except that ammonia and nitrite are both 0.
Stocking....is more art than science. A lot of people have experience with different stocking setups in different tanks. Usually once you start to indicate what direction you want to go, people start chiming in who are familiar with the fish you're looking at. There are stocking calculators and charts - generally the more sophisticated the better. Aqadvisor, while certainly not perfect, looks pretty perfect when compared to any chart. Even with aqadvisor, it is best to check the results with humans and not rely on algorithms.
Quarantining is essential, in my opinion, for long term success in the hobby. There must be stickies on it somewhere. Certainly are plenty of threads on it if you do a search.
The best thing for you to do is read up on the threads, then ask questions. This way, you will not be hearing information for the first time and will be able to assimilate it better.