Develope your own (or apply an existend) theory of investigated process. Calculate an electrotechnical model of your sample and use it to fit your data.
This way will help you not only to fit your data but also to understand what you have measured.
EIS is no more a dark art where you randomly do hit and trial with different circuits.
When you take an impedance measurement you have different ways to represent it.
Firstly form the bode impedance plots you get to know how many interfacial processes are taking place.
Once you know that, then you try to ascertain what all elements you might need for your circuit by analysing the bode profile.
However, since the frequency resolution is not good in bode plots, and also ohmic resistance contribution, you might need to perform correction for ohmic contribution.
But you normally perform circuit fitting on nyquist plots because you want the individual resistance values.
The question you asked is a very extensive one and you need a lot of experience for doing circuit fitting logically.
Below are some papers which give you a lot of information on how you can analyse your impedance profile and get useful inference from it.