Ok, for a very rough wild ass guess, start with 1/3 the total suspension travel available for your desired ride height. Do you even know what the total suspension travel available on your bike is? I know nothing about your bike, so I couldn't say, but your sag should be somewhere between 1/3 and 1/2 the total travel for your normal ride loading. If you're solo most of the time, then you only need to adjust for your riding weight (full gear). If you're resourceful enough, you can measure your total suspension travel yourself. You need to remove all weight (including the weight of the bike from the suspension. Mark that. Then bottom it out and mark that. The difference is your total travel, and your desired sag will be somewhere between 1/3 and 1/2 of that. Seriously, this is first grade math and a 100 level engineering class. My FJR is set at about 42% of the fork travel and 35% of the rear shock. I've found I like the front more toward the middle of the available travel. Of course you know that sag is only the starting point in setting up your suspension, right?