Best practice/Decision Tree on containerization

Hello all,

Please can you guide with your view and experience, what is the best approach to containerize an existing application, in term of methodology? Is there any decision tree, I can refer for selection of application/technologies for containerization.
Questions looks quite high level, but I am looking for a guide of generic “best practice/Decision Tree” on containerization.

Thanks for your help.

Thanks,
Kunal