Depends how big of a change you want to make. Some adjustments make a big difference to handling (like diffs, shock package, etc), and some adjustments are more for fine tuning (like camber angle, toe angle, etc).

The more testing you do in various track surfaces and conditions, the better you can anticipate what a specific setup change will do. Not all changes do the same thing in all conditions. To add to that, the same adjustment made on two different brands of car may not necessarily translate to the same feel on the track.