Above is correct.
Use standard settings when you first get a bike so you get a feel for what the designers intended.
Change the fork oil. Do this at least every year. It only takes 60 minutes to do.
Remove the swing arm and shock linkage bushes. Clean and grease. Do this every year - again it only takes 60 minutes.
Set suspension sag to 1/3 total travel when stood on the bike in riding gear - have a friend help, check it a few times to get a good average, and get it mm accurate!!!!!!!!
Rear shocks should be serviced/rebuilt but it is difficult to tell when they are due. Every 2-4 years would be normal. Tip - your shock is likely to have a rebound damping adjuster, unscrew it to make the car park bouncing up and down test damping overly-bouncy-no control-highspeed kick back-fast, turn it in 1/2 turn, feeling for some speed control coming into it's action, turn adjust in again, and feel the difference, turn in and test again, and again.
Rebound damping makes a HUGE difference to traction and slightly slower normally gives more traction. You are looking for a smooth but controlled rebound action and not too fast.
If the rebound adjuster makes little or no difference your shock needs a rebuild.
Ralphy