Here's a few more:
Don't try and cram a gazillion species into a small tank. Keep the number of species to a minimum. A tank will look much better with proper schools/shoals of 2-3 species rather than the bare minimum of a gazillion. Gazillion will eventually be an actual number if the US's debt gets any higher!
If you want more species, get a larger tank. I personally like 3 species per 20g, see below for the reason why. I'm talking slim-bodied, minimal waste-producing small fish. If your fish are bigger, then that's a different ballgame.
Don't purchase all your fish species to occupy one strata of the tank, instead try to find species that will occupy different levels. It makes for a more aesthetically pleasing tank and tankmates will not bother each other so much.
When you are setting up a planted tank,
don't add your wonderful brand new upgraded lighting until your CO2 is at the level you want it too be. When it's there, then add lots and lots of fast-growing stem plants and then turn on your lights. You'll have less algae to deal with. Once your tank is stable and algae free, you can aquascape the way you want.
Don't plant anubias or java fern all the way into the substrate. These plants have rhizomes and if water circulation is cut from the rhizome, it'll rot and your plant will die. You can cover the roots, but leave the rhizome above the substrate. Better still, attach these plants to rocks or wood.
Don't move cryptocorynes around too much in your planted tank. They don't like to be disturbed and they could melt on you. This is called cryptocoryne disease.
Now,
don't toss a melted cryptocoryne right away, most of the time, if the roots aren't too badly damaged or shocked from the move, they'll grow back right as rain in a few weeks.
Of course, you are welcome to disagree with anything posted here. I am definitely not the be all and end all of tropical fish keeping.