One way is to warm the engine up and when it is warm, lean the top end by 1/8 of a turn. The drive it again and you should see a slight improvement in performance. Keep doing this until it doesn't get any better. Then richen it so it is just before this 'perfect' setting and this is right for running. You can take it to it's best, but this is usually too lean. Remenber no to worry about the low-end at this stage.