Thank you for the opportunity to help you with your question!
"for a punishment to attain its end, the evil which it inflicts has only to exceed the advantage derivable from the crime; in this excess of evil one should include the certainly of punishment and the loss of the good which the crime might have produced. All beyond this is superfluous and for that reason tyrannical" - Todays concept of proportional punishment according to crime derives from there.
Some rules that Beccaria writes about are that: laws must be set by legislators, legislators cannot judge persons, judges in criminal cases cannot interpret the laws, laws must be clear and in need of no interpretation, offenders must be judge by its peers (half of the victim half of the criminal) - All of the above concepts are the pilars of todays penology .
"Laws should forbid leading or suggestive questions in trial, no torture to receive a confession and the right for the criminal to defend himself if certainty is found, but not so long as to make the punishment not prompt. " Well needless to say that those notions where adapted in todays penology where suggestive questions are forbitten and so as leading the witness . Confession derived by torture is banned and inadmissible to court
Finally individuals should be punished for attempting to commit a crime, accomplices working together on a crime should be punished equally, harsher the crime the harsher the punishment All those are part of Beccarias theory.
Please let me know if you need any clarification. I'm always happy to answer your questions.