Pack only the things you absolutely need. NEED, not want or desire or that might come in handy. If you still run out of space, you need to rethink either your planning or packing, otherwise you are looking at getting a bigger vehicle or a (bigger) trailer.
Pack the heaviest items in the bottom and between the vehicle’s axles. This optimises your vehicle’s stability and handling with its load. Keep as little as possible on the roof; it is best not to have anything on the roof. If you have to pack on top, rather keep heavy items inside your vehicle and light stuff on the roof.
You may have to compromise to be able to fit recovery equipment. These are typically heavy, but you don’t want to bury it right at the bottom if there is a good likelihood of needing it. Try being creative – perhaps you can pack it at the bottom in such a way that you can slide it in and out as needed.