If you're talking about the procedure itself, there's a guy on YouTube that shows it's much easier to get the machine in the air, pull the bottom retaining bolt on the shock, and swing the assembly out of the A arm. Then you stick a screwdriver or whatever through the loop on the end and can twist that the direction you need to adjust the spring the way you want. MUCH easier than banging your knuckles on everything while using a specialized tool trying to move the adjusting nuts on the top of the shock assembly. As for actual settings, it really depends on what you are looking for, your riding style, etc. Why are you looking to change the preload? What are you looking to accomplish?
The best way is to jack it up. If you dont have a spanner wrench for the shocks then you need to get one or it will mess of the notches on the ring body. If you use oil to help them move, please degrees the oil off the shock. Dirt will get in there and cause it harder to move the next time. Next, once you have moved them down to what you think is what you want for the correct spring preload, lower it back down. These is where alot of people go wrong, they dont roll the car/utv fw and backwards. (Also the weight of the passengers, tools and so on need to be in the there. This way you get the correct body weight to get the correct preload achievement). I like to start from ground zero as in Zero preload. If I end up with more then 2 inches of preload, your spring package is wrong and needs to be changed out. Best of luck.