A good way of demonstrating the basic principles of hydraulics is to join two syringes together with rubber tubing to make an watertight seal [see figure 1]. The syringes can be filled with water, oil, or just air. Pushing plunger A causes plunger B to move out and pushing plunger B in causes plunger A to move out. This works even if the syringes are not in the same plane. i.e. if the tubing is bent by 90° as long as there is no kink in the tube that prevents the free flow of fluid.
With syringes of different sizes it is possible to demonstrate how to multiply force [see figure 2]. A small mass on a small syringe can lift a much larger mass if it is resting on a bigger syringe. This is because the pressure in the two syringes is equal, but the surface areas of the two pistons are different, and force = pressure × area.