first off, set your sag for your riding weight ie how much you weight with your helmet, gloves, suit, boots on. 30-35mm sag up front and 25-30mm sag in rear is a good place to start. some chassis, like mine, like to ride a little deeper in the suspension travel than others. just something you learn. A general idea of preload is that if you press down on the bike in the middle (like at the back of the tank) both ends should compress equally and together.
Follow the above posted guide to how to set sag and then go from there. There's a lot of test and tune on rebound and compression. You generally want rebound set so that when you compress on either end it rebounds to the original position but doesn't go any higher and then sink back down. If that happens, you need to up the damping some. If it takes forever to nudge back up to the original postion, take out some damping. Compression is half a comfort feel and other half traction, but again they both take a bit of test and tuning.
Follow the litre
It's always Duc season in my book
Nothing like twins messing around between your legs.