Its not really trial and error, more educated guess work
There's a rough sweet spot for the point of influence as viewed against the sail and moving away from that in different directions will favour certain traits (usually at the expense of others). Moving the towpoint toward the sail or away (short or long bridle) will make the bridle more or less sensitive to both input and any shortcomings in the rest of the sail. After that you can make any or even all of the legs dynamic by various means so that you get a longer/shorter leg in certain positions to help with tricks.
The hard bit is developing an intuitive 'feel' for what's going on a hundred feet away just from the pull on the lines (that however has been the source of the dichotomy between those of us who design by feel and those who want to calculate but the archives are already full of that stuff...)