A couple things to help clear up some questions.

First: charging is still buggy and needs work by CA. Some things like only your first line in formation charging are (I hope) bugs. So you will not always get a clean/useful charge even if you do the right things. But still if you take time to setup and single click you'll get 80%-95% success rate vs. a 5-10% success rate by just wildly and chaotically charging your Calvary around the field.

Second: if your unit's are already inside the charge radius and you single click, they will begin the charge immediately. so if you run (double click) them inside the charge radius, and they are still out of formation when you single click, the charge will still probably be crap even if they lower their lances. Try giving a facing command with your moves so when the reach that point they should line up quick and be ready for a good charge.

Third: The only time a unit will stop before the charge is if they have been given the single-click "engage" order outside of the charge radius. Once they reach the charge radius they form up quick and then charge. Again, if they are already inside the charge radius when you single click they will try to immediately charge w/o forming up. so if you're moving a unit from one place to another and want them to be able to get a good charge I'd recommend giving them a facing order with their movement and trying to get them to line up just outside the charge radius.