I use a matrix for St Davids BTC and score each sections easy, medium and hard for each route - then try for a 1/3, 1/3, 1/3 .
I do this before marking the trial out so you know what each sections needs to be before you get there - its easy to get carried away once you start sticking the markers in.
We have graphs from previous events supplied by ACU so we can compare theoretical with actual for past sections. Also get somebody else to rate the section to get balance view.
I also try and avoid having hard on all routes in the same section -ie hard on champ would then try and be easier on expert route to avoid bottle necks. (terrain sometimes dictates that this is not possible)
Ideally 15 to 20 marks is ample for the winner but also try and avoid real stoppers that the very few can fly through but the lesser will be upside down on. Several tricky bits rather than a do or die.
it doesn't always work out and things you think will be hard are easy and that simple muddy bank suddenly become the test of the trial