Having girls that are young and related, or at least used to living in the same tank, is also a good way to start. Mine were living in a tank at the petshop and travelled home in the same bag (not a good idea, but it worked for me). I've not had any fighting with my girls, even after adding a tiny little unrelated shrimp of a girl, less than half the size of the big ones. I believe that's fairly exceptional, though.
Java fern, rotala, ludwigia and lacefern are all great plants, too. Using driftwood with plants on top of it can help give you extra levels. :)
Also in my sorority I have Endler's Livebearers (tiny cousins of the guppy, extremely cute and colourful - the females are bigger and less colourful), ember tetras (smaller, slower and more peaceful than neons) and cories. My girls have had no problems with any of these. :)