Mounted combat: Charging and Overrun

[Brigma]

I am getting to make a mounted combat specialist, not sure if fighter or cavalier, but what I am most interested in is how charging works in comibnation with other bonuses you getting from the mounted combat feat tree, like Trample. Also important is improved overrun? And can you overrun as part of the charge, as in I get my lance attack then trample you with my mount? The question(s) I have are kinda vague (sorry) but I just want to understand how the rules interact, especially if I had a unique mount that already had Trample or the Improved overrun feat itself.

[Brigma]

Sorry for asking the same stuff as many of the older questions but it never seems to have any definative answers.

[mythos2005]

I had a DM once that allowed me to both charge and overrun in the same action. I was playing a Dwarven Fighter, who at the time was enlarged. I'm not sure if the same could apply to mounted combat, but I don't see why it shouldn't.