When machining, what do we apply to get a good finishing and with accurate measurement?

Hello Emanuuel , there are many good practices you can follow in getting a good finish and precise dimensions. Your quesion is so general so I think it's so difficult to answer unless you go more specific.

But in general, the tooling you use in machining plays a great role, the machine too, the fixture and in many cases the machining strategy you apply and the sequence of the machining operations used. In case you use CNC, then the CAM software is a killer point and the CAD in which the original models were generated in plays a role , there are Class A and Class B surfaces at the end :)

Out of my experience, machining things is an art that needs experience, the way you do it given your own limitations makes it so relative and is key to getting whereever you want to get with your part.. 

I personally work in a CNC enviroment, a while ago, I discovered that I can get better finish quality with the same tooling when I go trochoidal in milling (since my CAm supports this) or when I increase the number/distribution of points when I use a spiral milling strategy for finishing in milling .. There are a gazillion ways for doing that so I think it'd be easier for me and everybody  if you tell us more about your setup in order to get a better answer.

Best luck

Fadi