How would I resolve forces on a slope?

First pick a set of axis to use. This would be in the directions of which the majority of the forces follow. With the forces which are at angles to the majority of the forces, create a triangle of the horziontal and vertical components of them. You can then use Sin, Cos or Tan to work out your components in a certain plane. Then Use F=ma and group the forces into directions as a net force equation. The forces are then resolved.