There is a low speed screw, a high speed screw, and an idle screw. Start with the low and high 1.5 turns out and set the idle screw so it just starts to open the throttle plate. Turn the idle screw in until the saw will start and idle, then adjust the low screw till the idle speeds up, keep adjusting the low and idle till it starts to idle poorly then go the other way so you have a nice smooth idle at a speed where the chain just barely stops creeping. Then adjust the high screw will it just stops 4-stroking then back it out 1/8 turn or until it 4-strokes at WOT but clears up when cutting. Once the high is set, go back and adjust the low speed screw till you have good throttle response without it loading up and dying at idle, you will probably have to adjust the idle a couple more times while you do this. Once all three have been set go cut some wood and go through the whole process one more time with the engine hot then it should be good to go.
It's a balancing act between the three, low and idle fight each other, low and high fight each other. The goal is a saw that is rich enough at WOT to 4-stroke out of the wood but run clean when cutting, have good throttle response and idle without the chain creeping and won't load up and die if idles for 30 seconds.
I definitely recommend a pressure/vac test. leaking crank seals are common and will burn up a saw, they also make a saw very difficult to tune and that's often my first indication that I have an air leak. A good running saw will all of a sudden fall out of tune and I have trouble keeping it in tune.